Canon has recently disclosed the Rated Shutter Life for all EOS models:
Model - Rated Shutter Life
Canon EOS Digital Rebel XS / 1000D - 100,000
From -
http://photocamel.com/forum/canon-fo...xpectancy.html
I agree with Jimmy though, if you can afford it, it's probably worth replacing it, as you don't want it to go when you need the camera most.