I never have issues with sticky buttons. I guess it's because I don't usually touch the remote with greasy hands. Also, I've seen people who's remotes stick because of nicotine. Good thing I don't smoke cigarettes anymore!
I have found that once the remotes do get sticky (I've had people give them to me to try to fix) it's nearly impossible to get them completely back to normal. I've tried cleaning them out (without opening them) and what happens is they quit sticking for a few hundred presses then they get back to being sticky. Sticky remotes are annoying as hell though I'll tell you that!