By that, I mean this: have you ever finally just given up on a genre and scale altogether? I have, four times.
I gave up on 15mm Napoleonics because, well, there was simply no point. My friend Tom has literally tens of thousands of figures from all the major combatants of the era and many of the minor ones. And if that's not enough, Marc has a few thousands more. So there was simply no point in my building up a force of Austrians (and going snow-blind painting all of that white-on-white in the process). I gave Tom my few battalions to bolster his forces, plus a hundred or so unpainted AB miniatures.
The second was also Napoleonics, but this time Age of Sail ships. I played a game of Close Action about 17 years ago with Jeff Hunt (?) who made (and still does, I believe) 1:1200 (?) scale models of the ships. It was a lot of fun. I bought a few ships and painted them. Bought the rules. Never played them again. Finally gave the ships away (Game it Forward!) at a Historicon about three or four years back to a fellow TMP member who thought he might use them. The rules are still in their box, on the shelf.
I gave up on Warhammer Fantasy a long time ago and gave away large sections of my High Elf army. This would be about 1995. Then I got back in and bought Bretonnians and Lizardmen in a boxed set. Sold off most of the Bretonnians about seven years ago, still have the Lizardmen (for VSF). Now I am back in again, slowly building an Empire army (as in, for the past five or so years and yet to play a game) and determined to ignore the existence of the Age of Sigmar.
I also gave up on Warhammer 40K and ditched my Eldar. Sold for a pretty penny, as I had some things that were not common even then, old Rogue Trader stuff like Harlequins, War Walkers, Dreadnoughts, and the gun teams. I also had the first iterations of the Aspect Warriors, one unit of each to stiffen up the Guardians that were the mainstay of my army. It's been so long I am not even sure which Craftworld they were supposed to be defending. Aliatoc, perhaps? Blue and yellow, at any rate.
Technically, all my other projects are still 'on the boil.' And that's a lot of projects, in terms of genres, scales, and forces. Oh well, better than wasting my money on women and whiskey, right? I know my wife prefers it that way...