The crank brgs. last forever. I/we replace them when the motor is split just cuz it's the common sence thing to do.
The only thing that would enter into this is the lower rod brg. you may want to see if there is any up/down play in it. I don't feel that it would cause all this trouble tho.I've seen them with .030 play and run like new.
I know you keep the filters clean, but what exactly do you do to them?
Well, I may be gone for a few days so I'll explain that::::
I use Bel-Ray filter oil. It's thick like tar and comes in a qt., like motor oil. If you are using a spray filter oil, then I'd consider that to be the problem.