What self-interested incentives did white Northerners have to oppose slavery?

[Whack-a-Mole]

Of interest may be a thread I started 15 years ago asking how long slavery in the US would have continued had there been no Civil War. Interestingly, most were of the opinion that it was a broken economic model and not profitable enough to have continued for much longer and likely would have collapsed on its own within a decade or two.

How long would slavery have continued without the Civil War?

Assume for this thread that the Civil War never happened in the United States. That the Emancipation Proclamation never happened. Imagine the country continued on with slavery allowed as an institution. How long do people think slavery would have continued as an “accepted” institution in the United States (or at least parts of it)? How do you think change might have occured? For the sake of argument the only method prohibited in this thread as a mechanism to end slavery is military interven…