Hi Richie!
Sorry for the delay in answering.
The one good thing about failing sealed bottom brackets is one really can't do much harm to the unit itself -- it is already damaged and just degrades from there and the unit is unrepairable and ultimately disposable anyway.
The only real concern would be seizure (it has happened to me once when a ball bearing split and the pieces blocked the race), but that is generally rare except in advanced cases. More likely, the spindle will become noisy, pedaling friction will increase to some degree, and the whole assembly will wobble. This last is the most problematic in terms of causing collateral damage, as it can be severe enough the chain will begin to wear the chainring teeth. I wouldn't want to ride very far of there's much more than 2mm runout at the chainring when pedaling. You should be able to go awhile, but I wouldn't delay too long before installing the replacement; you might find yourself in a worse place when it finally lets go.
Safe travels, Richie
All the best,
Dan.
