I've not seen anything to indicate the sensor's deteriorate over time, and as there's no moving parts, I don't see why this shouldn't last. I do believe LCD
panels can deteriorate over time, but this can be replaced.
The biggest problem is most DSLRs simply get used more than their film counterparts - in my case by a factor of 10. And as the shutter is probably the most critical mechanical part, this usage will mean aging is accelerated.
When I bought a D30, I read that Canon tested the shutter for 30K actuations. I thought "well, that will last a while". Turns out I shot 30k frames in just over a year. Last July alone I shot 10k frames. Eventually most shutters will wear out, and the elapsed time before this happens is going to be shorter than for a more lightly used film camera.
Couple this to the rapid devaluation of old models, and the effective lifespan of a DSLR is going to be shorter than a film camera. Already I suspect it must be close to uneconomic to replace a shutter on a D30 (ie. makes more sense to replace the camera). I figure on a working life of a well used DSLR to be, say 5 years.
Colin K. Work, Pixstel