Ending poems

First off, congratulations to all the people making decisions now, and especially to the people who have already made their decisions, and joined us on The MFA Chronicles.

I'd like to take advantage of the heightened site traffic to pose a hypothetical question or two about poems. Someone asked me this question that I'd like to pretend I have an answer to, but also find myself asking: When do you end a poem? (By this meaning when do you know a poem is finished, but in the generative sense of it being done on the page more than in the sense that you've made your last revision.) In other words, where do you stop discovering?

I use a couple strategies to tell when a poem is finished. The first is just stopping when it feels done, then taking a break from it and coming back when I can look at it with fresh eyes. Usually when I look at it again, something new needs to happen.

There's also working until discovering what the poem knew that I didn't, and then revising with that discovery in mind.

Another useful strategy is to ask, at the end of a poem, "and then?" If that's a legitimate question, the poem's probably not over yet.

I guess the poem should be understandable in terms of emotional purpose/narrative or meditation making sense/argument being finished/that feeling of being punched in the gut by the end, but what I'm really looking for, above all those other things, is surprising myself.

If I'm being super hard on myself though, I might ask, "Can/should a genuinely potential reader say 'so what?' to these poems?" What I really mean by that is if the poem was in my first book, would I not want the reader (trying to decide whether to buy my book) to open my book to that poem?

What do you all think? How do you know when you've reached the end of the line with the poem on the page?