Thanks guys for the feedback. The bike is a 2012 Madone, but it's new to me so I have no idea how old the BB is. Best guess it's original. I'll probably pick up a new one on my next cheque, but it's good to know that I'm not likely to hurt anything else by riding it a bit too long.

Oh, and if I wasn't clear, the mechanic was saying that the BB had 1000km left in it, not that it was going to go after only 1000km. I'm a newbie but even I would have found that a mite suspicious.