For those of you who have (by accident of course) left screws in place too long, and the screwdriver slots are still able to be used, you can try a trick I learned from a golf pro friend. When they refinish clubs (epoxy glued) they will heat the screws. I use an older Weller electric soldering gun. Pull trigger to second setting and hold against the head of the screw. This does two things .... heat expands the screw and at the same time softens the epoxy. If you are lucky and the screw head isn't buggered up, you should be able to unscrew it before it cools down.

As hard as epoxy gets when cured, it is still "relatively" soft, and more heat will soften even more. Use this to your advantage. I learned the hard way when I laid a black plastic garbage bag over a rudder repair on my catamaran to prevent overnite mosisture. Forgot about it and by the time I got to boat next morning, the rudder had taken on a nice warp - right at the repair point, thanks to the sun's heat on the bag. Hard lesson learned!

Also, if you plan to remove screws, might want to consider buying square drive type. More expensive, harder to find, but so much easier to drive and remove. I'd ask for a show of hands from all who, while working on a slotted screw, slipped and had some wood "RE-finishing" to do, but can't count them from here.