RTS/strategy and RPG games i never do, as what fun is your ultimate army of doom, if you didn't save up for and build it yourself.
I do sometimes in FPS's when it gets to the inevitable "find an item to get past this door" or "this boss is invinsible until you find this tiny switch to turn the invinsibility off for a while"
I'm a firm believer of the "if you shoot it enough, it should break" school of thought