Lifetime. But we also need to handicap.
When I was swimming we used about a 4 to 1 ratio for swimming to running. Swimming a mile was like running four. Based on the winning times in Paris for the 1500s that holds up pretty well today (14.5 minutes vs 3.5 minutes = 4.14).
I took a look at the cycling individual time trials. It looks to me that the winner covered 32.4km in 36.2 minutes, or 1.69 minutes per 1500. So now we have an 8.5 to 1 ratio for swimming to cycling.
The revised question is, in your lifetime have you covered 248,463.5 (29,231 x 8.5) miles on your bikes?