Haha yea man, I feel you. For the first time I'm looking at my collection and starting to think that I have enough. I have one of the biggest collections on this board most likely, and its starting to get a bit overwhelming.
Luckily with the OT Star Wars characters starting to be completed and (I predict) the MCU starting to wind down after Infinity War I think my collecting will start to slow down after this year. After all a lot of my figures are from film series that are already over.
I think I have around 85 figures or so, and I'm certain my collection is pretty minuscule compared to a lot of others on here. Even at 85 though, I think that's way too many. I look at some of the figures I have in my collection and there's many of them I simply don't really get any enjoyment out of anymore, most of them being from the MCU. I'm looking at possibly wanting to ditch a lot of my MCU stuff, particularly from AoU. Not so much the Avengers themselves, but more a lot of the side character figures from it.
My SW collection is kind of coming to a close, as I pretty much already have the characters I want. TLJ Luke and Rey will likely be the last ST figures I get. The only other figure I'd possibly get is Rey from Episode IX to show her evolution as a character, but that's only if the film performs a major course correction that saves the trilogy and knocks it out of the park on all fronts, including her character. And as far as the OT goes, I think the only necessary figures I feel I'd need to complete a suitable representation of each film is just ESB Lando and RotJ Emperor. Though I don't like what HT rolled out for The Emperor, so that's a pass at the moment. Any other OT figure (Boba Fett, another Vader, Snowtrooper, etc) are mere maybes. I might decide to get one at some point, but they're not figures that I feel would be essential. PT wise, the only other figure I'd get is a RotS Obi-Wan.
MCU I'm done with after the one's I named on my list that I'm receiving this year, won't be getting anything from that anymore. And the DCEU I also think I'm done with for the moment, as the only other character I'd want from any of their upcoming films would possibly be a Green Lantern.
I really enjoy 1/6 collecting, always have, but I also at the same time want to make sure I don't burn myself out and like you said, have your collection get to a point where it's utterly overwhelming. In some cases, like the old adage states: less is more. If you just stick to franchises you really like and with the essential characters that represent those franchises best, I think one may tend to enjoy their collection more and also the excitement of purchasing and receiving a figure, since it's not something you do frequently anymore. Quality over quantity.