A few comments- The suggestion of having a weep hole is not a bad one but the Op has a cartridge BB with no bearing exposure inside the shell. So a weep hole won't change the bearing issues, maybe it will change the corrosion in the shell/threads. But this is not what the OP has said is an issue.

- taking the bearings apart and checking their races is fine if the BB was a classic loose ball type. But being a cartridge (and not one of the early and low cost Shimano units that was easily taken apart with those special pair of wrenches) the taking apart will be "tough". if the OP can do that level of service then he can also "pop" in a new set of bearings as easily. I don't think this suggestion is applicable here.

-Op still hasn't said anything about his size or pedfalling style. Or for that matter whether there have been other wear issues. Like chain or cogs. If the OP was so large/strong to wear out Bb's at such a fast clip I'd expect that the other parts would show problems too.

- My comment about water/pressure and bearing contamination is more for the reading audience. But I will say that using a high pressure washer is a commonly known way to wash out lube. Bearing seals are not designed to resist the pressures that a pressure sprayer can offer. If the operator is very careful as to where the spray is directed then the potential bearing damage is less. But any time a high powered tool is used it's up to the person to take due care.

-I suspect that something else is going on that's not told or understood. I doubt it's shell related as the Bb cartridge is pretty self contained and stiff enough to not have installation mistakes effect the bearings. The Op's latest comments about the old BBs being rough and hard to spin on removal says, to me, that it is bearing issues. So what can wear them? Go back to my 1st post and read again some of the factors. I am open to hearing other factors.

- It will be interesting to hear of the solution. Andy.