Just after opinions on the Ernie Ball Stainless Steel strings. I have always used standard Ernie's, D'Adarrio or Dunlop's just generally what ever is in stock at my local store at the correct gauge, and these have been nickel wound all the time.

Just wondering if being stainless steel you can keep a pair of strings on there for a few months to a year? Yes I know this question might sound dumb but sweat is extremely corrosive due to the sodium content.

Secondly is there a tonal difference or at the very least a playing difference. Again never used them so I am after opinions and consensus. Are they stiffer then nickel strings or hold tension differently? Anyways thanks for any info!!
A few months, maybe. If you mean 2 or 3. A year, hell no. SS strings will still get grungy and corroded, especially in the grooves around the wraps.

There are three common materials for roundwound string wraps (the core is always steel, so it's just the winding material we're talking about) :
  • Nickel alloy, the most common, usually just called "Nickel" though I'll explain why that's confusing in a second. It's what you're used to with regular D'Addario/Ernie Ball strings. We'll call it the baseline, which is useful since it tends to have middle of the road properties compared to the other two types.
  • Pure nickel, which is 100% nickel as opposed to the alloy mentioned above; these strings are marketed as "Pure nickel" strings, which is another misnomer, since it's only the wrap that's nickel. Still, there's more nickel in these than in regular strings, and it's the only metal your fingers will interact with. Their feel is generally softer and more flexible, and the tone is more mellow with the tendency to sustain a little bit more, or at least create the illusion of doing so. They will reduce fret wear, since they're the softest of the three roundwound types.
  • Stainless Steel strings have a stainless steel wrap; since it's more ferromagnetic than nickel or nickel alloy, these have a bit more magnet pull (readutput) than the other two types. This, along with the properties of the material itself, makes for a rather bright, cutting sound. Stainless steel wraps feel quite a bit stiffer and harder than nickel/alloy - because they are. They will also wear frets significantly faster than the other two types.
Wow that was really informative. That answers my questions perfectly thanks colin! I think I will try out some pure nickel wound strings and see how I go thanks for the help!