I have been playing for ten years now and have never built up great speed. I have been working a lot on technique and ways to play faster over the past few months. I have seen some improvement but not a huge jump in speed. Do i need to work longer or after ten years is it more likely an aspect I will always struggle with?
You just need to work on it more, especially if you've never tried to play at speed before.

Another thing to mention is making sure you don't specifically go for speed; you can't make yourself play faster, you can only make yourself play better. Therefore you need to make sure you're playing as well as possible and speed will follow in its own time.
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“A man who mistakes secrets for knowledge is like a man who, seeking light, hugs a candle so closely that he smothers it and burns his hand.”

It's hard.... I think there's a balance between pushing for speed and keeping your technique correct, relaxed, and proper. Also, you need to build up stamina which is really what will strengthen your hands in the long run.

I take a lick or exercise and I play it at a slow tempo like 50 bpm for 5 minutes continuously, and then I push the tempo to 60 bpm and play for 2.5 minutes, then 70 bpm for 1 minute and the 80 for 30 seconds. After a week or so and 70 becomes easy then I'll push the whole set up 10 more bpm and that's basically how I do it..... this style of workout is helping me with stamina, trying faster tempos, etc....

Hope that helps
The best way to develop speed is discipline with a metronome. Before you can begin to develope speed you basically need to be doing EVERYTHING right fretting and picking wise, if you have been playing ten years and don't think your very good, then you might be lacking in a few areas. Make sure When your running through scales (which is esential) Your thumb stays pointed straight up pressed against the back of the fretboard behind your second finger. Make sure all your fingers are coming in on their fingertips. When you pick make sure you are alternate picking, this is critical, and the easiest way to pick in my oppinion. If you dont alternate pick, then start working on it because think of this, when you alternate pick, its allways dow, up, down, up, down, up, the pattern never cahnges, even when you switch strings, some strings end up down picked, and some are up picked, but you dont really notcied because the pattern is consistent, the flow is very comfortable. if your not alternate picking then every time you switch a string theres a chance your hand will want to down strum the next string, and this could throw off the pattern, if you just get used to alternate picking, then you will never have to worry about your picking, you will become very fast with a metronome over time farely easily as long s your alternate picking. When you play your strings, use the tip of the pick, you have to really watch as you pick (do this at a slow tempo) and try and use only the tip as you pick, evnetually this builds into the subconcious through the constant repition of the scales, and you develop the ability for use every time without thought your even doing it.Dont let the pick move, my pick is always perpendicular to the strings, and that angele shouldn't cahnge either way, I also keep my thumb aligned with the strings when I pick. When you go through your scales a lot, what you want to do is start to have your fingers getting in place without having to think about it, eg. say your playing a G Major scale and you play the 3rd fret and 5th fret on the G strings, now when you transition strings to the A string, you should be so familiar with the scale that your hand will be in a position where your first second and fourth fingers are already hovering above the friets they are about to play, so that when it comes time to play then you just simply push down. you dont want bg movement with the fingering, the reason guys get so fast is because they get their fingers close to the frets and they have done the scale so many times there hands are literally going into position instantly as they get to where they are going, when go back down, one fast technique is to have your fingers already placed on the notes on the string, and just do pull offs, get to the next string, fingers press over frets in scale, and just pick pull offs. Once your sure your technique is flawless, then maintain that disipline with a metronome, and always play to a comfortable tempo, never strain.If your doing everything right, then you will gradual be able to cahnge speed and go faster and faster, but if your not alternate picking, or your thumb isnt in the right position, using your fingertips, eg any one thing is missing then your going to have a hell of a time trying to get faster without it, hope this helped!
Ok, since I know I'm gonna get pissed on if I link you to a very good article about building speed... I'll take the time to help you out... PM me if you want the link.

When you build speed, you need to EXAMINE your technique VERY CLOSELY. Take note of what both of your hands are doing. Usually your picking hand is actually slowing you down.

Ask yourself these questions:

1. Can I make my picking motions smaller?
2. Can I keep my pick closer to the strings?
3. Can I use directional picking instead of alternate picking?
4. Can I use inside picking instead of outside picking?

1. Are my hands relaxing after I play every note?
2. Am I tensing any part of my body unnecessarily?
3. Am I pressing too hard on the strings?
4. Can I hold my fingers closer to the strings?

Naturally, you probably don't know how to solve any of these problems, because if you did, you wouldn't be asking about building speed. But you should be aware of this stuff.

Now, this is what you'll need to do to improve these problems:

1. Decide WHICH of the issues I mentioned you will work on today (one at a time!). Decide also what speed you want to reach today.

2. SLOW down your guitar playing to playing ONE note every TWO seconds (that's very, very slow).

3. As you start to speed up (very slowly), make SURE you're focusing on the issue you decided to work on.

4. As soon as you start to notice the problem appear, SLOW DOWN.

5. Practice at that speed for 5 minutes... then try to go a little faster.

6. Repeat steps 3-6 until you've reached your goal for the day.

Once you go through this process for ALL of the points above, you will be much, much faster than you were before.