How do editors feel about poems that have very long lines?

each will vary in their approach.
the best advice i can give you is to pay attention to what they ask you to submit and how it should be submitted, having checked out some of their previous editions (if we're talking magazines/e-zines here) to see the sort of work they are currently promoting.

and ask yourself, if we're talking about your own work, why do you use long lines? do they play an important part in the poem for pace/'voice'/sound? would it be detrimental to your writing if you found a natural break-point whereby you could use two shorter lines instead?
 
When publishing Blue Angel Landing, we had to make font and point size decisions all over again to accommodate a poem with really long lines. One of the three editors, during this process, suggested we just ditch the poem.
 
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