You must be a very strong climber!

Out of curiosity, I did a search on this issue, i.e., bottom bracket bearings lifespan, on roadbikereview.com's forum. The guy I consider to be the "guru" on all things involving bike maintenance had the following to say:

"Your question is about like "How long is a piece of string?" The weather you ride in, how well your frame was built/prepped, and the quality of the BB will be big influences. If I had to replace BBs every 4K miles, I'd be doing it more than 2X per year. My last BB (Campy Record square taper) lasted 60K miles before I screwed up the install and cracked the flange on the RH cup - the bearings were just fine. My current (Campy Chorus square taper) has nearly 58K miles with no signs of distress.

If you turn the BB axle with a light touch of your fingertips (cranks off) and there is no binding or gritty feeling, then you're fine."

There were a number of other comments about how recent changes in BB design have decreased the lifespan of the average BB, but the sentence bolded above is what I think deserves to be emphasized. Regardless of the average lifespan of a BB, it pays to know how to evaluate your own components. I prefer to run these tests myself or have DH do it because, well, I've been sold a bill of goods by too many bike shops. But that's just me.....