All DSLR's will have shutter actuation ratings - this is akin to the materials used in the making of the moving parts and how many typical actuations it will work for. YMMV, but from what I understand the ratings posted are quite conservative (meaning you'll likely get many more than what is rated).
Typically cameras are rated for 100,000 (most DSLR's), 150,000 (D700) and 300,000 actuations (D3 series).
In doing a quick google search the D3000 is rated at 100,000 actuations - which is the same as all the Pentax DSLR's (that I'm aware of).
Hope this helps!
c[_]
P.S. Here's the link I used to get D3000 actuation rating:
Nikon D3000 Digital Camera Comparison - Full Review - The Imaging Resource!