The only save I have stopped playing was one that was lost because it was on another computer, another account.
I have 2 MP saves with the wife and 1 solo.
One of the MP saves is a forest farm that we just started up somewhat recently, and we're only half way through summer year 1.
The other MP save is 4 corners, year 5, and I plan to do... everything in that save. I just recently, finally, got the Full Shipment complete. Got married, no children yet. Besides that, the only big things I have yet to do are Master Angler and 1 of the monster-slayer goals. (I'm speaking literally here, too. I have reached the point where the only thing I can spend my millions in the bank on are more Statues of Endless Convenience(tm)) I will have literally EVERY hat in this save, this I swear. When I accomplish that... maybe I'll lose interest.
The last save, my single solo save, has a ways to go. I'm only fall year 2. Completed the CC. Haven't completed the Lost Bundle yet. Haven't gotten married yet. I still have so much to do ...I have to get all the dateables to 8 hearts, date them all, and trigger the group events, before I marry. And then, here I still have to get married, get the content only available from marrying that person, divorce, marry the next, get the content, repeat... and when I'm done with all of them, ask Krobus to move in and use the shrine so that the exs all forget me and we can start over.
I play the solo whenever the wife isn't available for playing one of the MP saves. She also has a solo riverlands farm she plays when I'm unavailable. The MP saves, we go back and forth, now that we have the both of them. So, yeah... no real restarting. Just different games with different styles/strategies used based on the individual farm, and we pick which one we want to play, and don't have any we don't play any more yet.