I tend to stick to short and sweet solos, because my problem is playing the damn thing without making a mistake. Stick me in front of a Bach fugue with no audience and I can get through to the end without a single glitch....but put me in front of an audience, or hit "record," and this annoying little voice starts saying "you're going to screw up any minute now....any minute now." And usually I do, like a bar before the end.
As for composing guitar solos, I whistle them first nowadays. I've gotten to be a pretty good whistler and my philosophy is, if I can't whistle it, it's not worth playing.