Are you sure they don't mean that oil is *also* leaking from the crank seal?
(whups- I'm assuming the crank seal and not the cams)
It's hard to imagine *that*much*oil* getting past an old seal.

The timing belts are usually recommended to be changed at something like 90k miles.
It's normal to swap out the oil seals (at least on the crank), the water pump (while it's accessible at the same time), and possibly the belt tensioning assembly during a cam belt replacement. A garage might throw on the rest of the belts and hoses, too, to pad the job up a bit. Usually it's not a bad thing to go along with all these recommendations, although it's highly dependent on the garage.