I gave up on Voyager a few episodes into season six, when I realised I’d given it moooore than enough opportunity and, no, it wasn’t going to get any better. I adored Farscape (and still do) and I think that show ruined Trek for me at that point. It was just everything that Voyager wasn’t.
I also gave up on Enterprise sometime around season three. I’d struggled with it up until then. I just never particularly warmed to the cast or the writing and Trek was feeling so very tired at that point. The attempt to arc up the third season was a step in the right direction but just too late for me, I’d checked out.
I’ve yet to watch SNW season three and have absolutely no enthusiasm or impetus to do so, so I guess I’ve pretty much given up on that. The shark jump point for me was really the musical episode in season two (which I’d been on the fence about until that). Whereas many loved it, for me it underscored how gimmicky and vacuous the show actually is. The character arcs were all basically “who fancies who”…and I realised at that moment I was kind of done. I’ll probably watch it eventually out of completion, but I’d rather rewatch my favourite old Treks again first.