Hi ...

I have been practicing the following techniques for a while now (about a year) ...
and have made some progress. I was just wondering how long it would take to become really good at them. By good I mean as good enough to play a lot of fast licks like Zack Wylde, Paul Gilbert, John Petrucci etc.

1. Alternate Picking
2. Legato
3. Tapping

I practice exercises for each one half an hour daily ..so thats 2.5 hours of practice daily.
I mainly follow John Petricci's rock discipline, but I also throw in licks I find interesting and hard to play
It's important to note that those guitarists have been playing for a long time. I am pretty sure they've all played longer than 20 years.

As for how long it will take, see the above answer.
It also depends on how well you practice, how quickly you learn, and how quickly you can identify problems with your technique and correct them. You can't put a time on how long it takes to get good - what you can do is set yourself mini-goals that are achievable, based on your own knowledge of how fast you believe you can progress.
As long as it takes
Actually called Mark!

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As long as it takes

I second that. You must allow yourself the freedom to progress at your own pace.

Consider: Every bit of time and energy you spend worrying about whether you're progressing fast enough is a bit of time and energy you can't devote to actual practice. You'll only slow yourself down by worrying too much about how long everything is taking.
"Music is all about wanting to be better at it."

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He was talking about me.