Back to the original topic, I have often felt the same way, that the work never actually gets "finished" because I edit and edit and edit.
I'm not so certain that wouldn't also be the case with strict form...perfecting word choice, getting the most bang for the buck out of each syllable, being certain to use more poetic techniques than only rhyme and rhythm (which are challenges for some of us anyway, but for a form poem to be memorable for me, it needs to employ other poetic magic tricks).
I would behave just as obsessively over a form poem as I would a free form, and because of the additional challenge of sticking to the form, it would require more, not less, editing.
Really though, I don't think the answer is as simple as changing what you write. I think it is about trusting that a piece is done and how you know when. I would tweak mercilessly for a days, then let it rest. I've gone back to some of them now (much much later) and can look at them with fresh eyes.
Perhaps you need to get it to where you are at the "print it out" stage, put it away somewhere out of reach for a week before you are allowed to take a red pen to it again.
Also, i think that kind of editing is definitely a learning process. You are developing your voice when you do it. Don't limit yourself,. let yourself edit; Perhaps you are just the type of poet who takes longer to write the work you want to write. Some of my poetry has gone through dozens of full drafts (not just word choice and punctuation tweaks). some of them just take longer to write than others.
Keep a clean copy of the piece pre-edits. Sometimes we over edit and lose voice and/or other elements of the poem that make it work before we get our big paws on it and in the way.