From the picture it's very hard to tell but it doesn't really look that bad to me. I've seen much worse put back into operation. I don't see any pitting or brinneling in the channel at all in those pics.

Yes, there is some wear in there but the bearing channel looks good for the most part. There are some spoils to the outside where material has migrated to the sides that look ugly but it looks like it is outside of the edges of where the balls actually touch. From that picture it looks like there is still plenty of life left in that spindle(s). I'd personally just rebuild with new balls and grease and keep running them. What's the worst that can happen -ruin them and/or the cups???

If a rebuild yields smooth operation then let them run until they get much worse than that. You aren't going to hurt the BB shell in any case. This is a bicycle not a high RPM engine. You aren't going to get a seizure which will spin the races and ruin the BB threads or damage anything outside of the bearings themselves.

When it finally does give up the ghost (there will be plenty of warning) do as others have said and just replace the whole BB with a sealed unit. I think, looking at those pictures, that it is a bit premature for that.