Um, to be honest.... I never lose inspiration.  For that to happen, I'd have to have already finished all the things I started, all the things I designed but never started, and all the things I've thought of but never sketched or designed.  Oh, and tried to make my own versions of everything in my "absolute inspiration" collection.  I don't think I'll live that long.  I'm just hoping I'll have enough time to acquire the skills to make half of it.