The only time I have ever done my own alignment was when I bring in my cars/trucks to work on the weekends. The only time I whip out the tape measure is to get it close to 0* for toe and camber, just so I could drive it to the shop.
I say just be careful about being a gung ho about doing your own alignment. Just remember you are gambling with about $400 worth of front tires every time you do it.
Most shops I know offer a 5,000 mile/5 month warranty on alignments. The day the alignment is done, the smart ones come back before the warranty is expired to get a recheck or adjust. Just be sure to get a before and after print out. It also would be wise to "watch" them do the work whenever possible to keep them honest. I know many cheats to adjust the figures. It would also be wise to get the tires from them as well, just so the salesman doesn't pull a fast one over you when the tires wear out prematurely.