Too much is made of the distinction between segues and medleys IMO. Even with the former the original structure is not preserved, in the strictest sense, since there are altered or omitted sections (namely the intro, the coda or both).
As for me, I do segues, quick citations and everything in between including mash-ups. I strive to keep it interesting and creative, with fluid transitions and meaningful juxtapositions, and rely on my judgement (as a listener first and foremost) on what to shave off the original composition. If I find significant melodic or lyrical value in a part of the song believe me, I'll be the first to want it in, even if the medley chunk represented by that song ends up longer than the others.