A few years back, I decided to embark on a rewatch of all of Trek in rough chronological order (meaning ENT then TOS, then the rest of the series roughly as they came out). In some cases this was a rewatch (I had watched TOS in syndication as a child, and then TNG, much of DS9, and a small bit of VOY as it came out - plus a later rewatch of DS9 as an adult on DVD), though in the case of much of VOY and almost all of ENT other than the pilot, it was me watching for the first time. It was helpful going through everything over a relatively short period (less than two years) because now I know what episodes I'd actually want to rewatch, and what I never want to watch again.
More recently I've watched a bit of ENT again, since it had been the longest time since I had seen it, and I didn't remember much of Season 1 that well. I've been stalled out in Season 2 for awhile even skipping the worst of the worst. I think I have decided that although it's probably objectively a worse series at the beginning, I enjoy ENT more than VOY however, because feeling anger towards a show is at least more of a reaction than apathy.
I will probably rewatch DS9 again at some point in the next decade. I will rewatch certain episodes of TNG and TOS, but I see no reason to watch everything given the quality control issues across both shows and the lack of continuity. I don't anticipate ever watching VOY again, unless my kids really want to when they are older or something.
I do not plan to rewatch DIS. Much of my enjoyment the first time around sprung from wondering where the journey would take me. Given the ending of the season was rather underwhelming, I think it would make my impressions of the individual episodes more negative.
Re-watching is definitely better when you know what episodes to skip. I'll end up in a situation where I'll be like "I feel like watching this one!" or "I feel like watching that one!" and I'll watch it, and maybe a few, then I'm all set. So there's no realistic way I'd personally sit through 700+ episodes.
I'm about to re-watch late-DS9 soon-ish. I say that and it'll probably end up being months from now.