It looks a bit short to me as well, specifically that front shoulder, but with you never having the intention to shoot spots, the extra muscle you are using with that front shoulder has time to recover between shots. You obviously have enough muscle structure as well to support what your doing.A bit longer of a draw would maybe make your pin float pattern a bit more consistent, though it would likely occur over a wider area. I like my draw a bit longer so I don't load that shoulder, I can't consistently do what your doing......I'm all over the place and fall apart quickly f I don't stretch that shoulder out. To compensate though, I do shorten my DL by a good 3/16" or so for 3D events that I know are going to have a lot of up/down hill, because I cannot stay behind my "preferred" DLas well as you probably do on the hardcore up/downhill shots. Last year I went a full 1/2 short to Harrisburg because I knew that course would give my normal form a beating.

With all that said, what your doing obviously works for you and is obviously VERY engrained in your muscle memory and subconscious. It would likely take several thousand shots and 3+ weeks to really change what your doing, and I wouldn't consider this unless you were considering other venues of the sport that would force you to shoot a LOT more shots in a short amount of time (indoor/FITA).

Edit*** - Dave C. has good form for field archery. Remember that he is primarily shooting on the most hardcore up/downhill courses at up to 80 yards. Yes he's short, but I'd bet $100 that he is tailoring his DL to fit the course he's shooting, and lengthens it out when he knows the courses will be flatter.