I recently got injuried running and now work out at the Y with my Shure E2c's. . .
The first time I used my preferred, foam sleeves. That was a really good idea, until afterwards, when they were so wet and absorbed that they didn't act like foam anymore! It took days for them to get back to foam qualities and they still didn't act new. Good thing I have extra of them. So, I thought, I'll use my soft sleeves.
Even worse of an idea. The plastic sleeves don't have a perfect seal, so what would happen, as my ears sweat was:
ear drum > small buildup of water > headphone sleeve.
The water wanted to evaporate out, but was kind of being trapped in by the headphones, until, I guess enough pressure accumulated and my ears would pop. That was incredibly annoying and once they started doing that the headphones had to come out for the entire workout.
Recently, my solution has been to dedicate a pair of the foams for workout only. Yeah, they are disgusting, but I don't care too much. First, I get a real, real good seal at the beginning of the workout, so that water doesn't really come into my ear. Then, I don't take them out. If they start to hurt or something, of course take it out, but once they come out once, that's all for that workout; you can't squeeze them enough to go back in and your ears are too wet. Once I finish my workout, I use my towel and squeeze on the sleeves. I do believe this reduces their life span but it's a better for them than keeping water logged inside of them until next time i work out. I spend about a minute on each ear getting as much water squeezed out of the foam as possible, and that's that.
hope it helps.