In the case of digital cameras the old saying applies:

"If it ain't broke, don't fix it"

There's really very little in the way of preventive maintenance that can be done. Normally the first thing to fail will be the shutter, after you've taken somewhere around 50,000 shots (maybe 100,000), but that's just normal wear. There's no lubrication required and unless you're having a problem with the camera, just use it until it fails. You can then chose to have the shutter replaced (around $250 or so), or you can upgrade to a more recent model.

I'm sure Canon would be happy to do a "clean and check" on the camera, but it would cost at least $100 and really isn't necessary. If you want to check with Canon just give them a call.