Mild Engine Knock--how long will it last?

Good to be here.
My cars got 230,000 miles on it. 98 olds cutlass 6 cyl vin m. I use 5w 30 part synthetic and a quart of LUCAS engine treatment every 5000 miles.

My car has overheated twice. Once when the waterpump went out. Once when the serpentine belt tensioner failed. Car barely got into the red before I realized it, and pulled over. It has been 4000 miles since the last overheat, and I hear a single mild knock from the bottom end. I have heard other cars knock before, and this is milder than a severe engine knock.

I think the problem is a rod bearing. How long do you think it will last? Since I have the cash, should I go ahead and get another engine with low miles from a junkyard, or run it for another year or so?

Thanks in Advance.

Impossible to predict, If you pulled the pan down and checked the bearings you may get away with replacing the suspect bearing if the crank is ok, assuming this is the source of the noise.

230k. Only got 132k out of my 96 till the camshaft broke.

Update, Seems the engine knock was from a worn out timing chain. Replaced chain, knock went away.