I try not to pre-judge prospective photographs. Film is relatively cheap (I shoot only 35mm and 120). I'd rather waste a frame than miss a potentially worthwhile photo. While I don't shoot recklessly I do try to be generous.
That philosophy has rewarded me with at least a few unexpectedly good photos. And there have been a few instances when I've declined to snap the shutter and later wish I'd gone ahead and made the shot.
Like Neal I'll return to site or subject as often as necessary when I believe it has potential and previous efforts lacked only the right light or something else - preferably something I can control.