> it's not really feasible for the dating site distinguish between "will successfully date for a few months" and "will successfully date for a lifetime".

I think it is feasible for a dating site to figure that out, given enough data.

And I think the 'few months' figure is probably too high - they want to match people who will go on a few dates or a one night stand, then return to the app.

It's a pretty damn strong signal when a user matches with someone, exchanges phone numbers, then deactivates their account. The ML algorithms will be trained to do everything possible to avoid that outcome.