I think it lasted about 6 months before I completely abandoned it, but I had started to cheat even before then. The main reason I quit was "mission accomplished". I had made new friends, discovered some social activities I enjoyed and was generally happier. But also I noticed some downsides.

One was that people will exploit that rule, even if they don't know about it. That church group would have cheerfully turned me into one of their most dedicated and active members just by inviting me to all the things. They meant well, but I was sending mixed signals by accepting all their invitations even though I wasn't interested in their faith. Once I had been to a few events I had to start saying no.

Another was that once I had a bit of a social life going, I didn't want to let happenstance push me around so much. The choice was no longer between do this thing or stay home and mope; I started to have other options and I didn't want to just end up doing the first thing that presented itself.

All in all, it was a great way to change my habits, but not a good way to live life indefinitely.

I was going to specifically ask how the "joined a church group" went because that seemed to be the example that had the most potential for being a slippery slope to a more complete change of life than you may have been looking for.

I have a family member that pretty much went all-in on came-to-it-later-in-life religion. It really felt like their susceptibility to loneliness was successfully exploited.