How far can you go with a badly knackered BB?

[Crankarm]

I've only had to clean it and lube it and change a couple of rubber bits so far, the bike owes me absolutely nothing. This is the first mechanical job I've had to do on this bike. It's been a complete trooper so far

Well good for you. For me I don't look at cycling as a zero cost option. Everything has a cost. Components and consumables do wear out so there is a cost to maintain and replace them or a whole bike unless you never use your bike. There is no free lunch imho.

 

[Racing roadkill]

One of these days all of my bikes will kick me in the nuts at the same time, it hasn't happened yet, but I'm not getting complacent

 

[Gravity Aided]

I got my Fuji Touring bike through most of a season, but the chainrings were already worn, the spindle was going bad, and the fixed cup on the BB was seized. Provided plenty of hours wintertainment. I had to remove the moveable cup and knock the spindle out, seperating it from the crank spider after removing the chainrings, then I had to go to the Sheldon Brown fixed cup removal method, with a 5/8" bolt, 6 big lockwashers, and 2 5/8" nuts, after soaking the cup for a weekend in penetrating oil. So yeah, i'll be splurging for the sealed BB. I already had a replacement crank, as I wasn't getting along with the step and a half plus granny gearing a lot of old touring bikes came with.