RE: Welcome to Club SAITO !
I find if the bearings were not seated correctly and you tightened the prop nut down enough to seriously bind the crank then likely you pooched the bearings. To add that much drag you would have deformed either or both the rollers or bearing races.
It may not seem like it if the bearings are then seated with the correct spacing and everything tightened down, but I can almost guarantee they will fail prematurely.
You do place some loads on the rear bearing if you use the crank to install it, but if you avoid banging it in place then it should survive. A couple of pointers I've found over the years are the inner bearing races should NOT have to be forced onto the crank. There should be a tight fit, but with both at room temp you should be able to install and remove the bearings with your hands only.
Also, I sometimes fit the rear bearing to the crank before inserting the assembly into the case. Even with the front bearing removed you can get a good indication of alignment. Otherwise trying to see if the bearing is going into the case straight can be difficult. If heating the case you can even grab the end of the crank and pull then into place or lightly push the back end of the crank/bearing pair down to seat.