Ellasmum, all photographs will fade and the paper wil get brittle over time - just look at ones from your own childhood.
Colour photographs are one of the few things that fade even out of the light.
HOWEVER, digital inks/paper from ones you print out at home are much more fugitive (sensitive to light) than the inks and paper traditional processing uses, so ones you print out yourself will have a much shorter life (12 years is probably a fair estimate).
You can get special photos printed out at a processors from the digital file using the standard ink and paper - they will last as long as regular photos (30 years if in light, probably). For super super special ones, Fuji do an archival paper and ink which they say have a 100 year life span.
But, the digital original will not have deteriated (unless you leave it on a disk or CD too long - see below), so a new print will be the same as the original.
While I'm on my hobby horse here, if you want photos to last - get a copy made for the frame and keep originals in an album; use 'traditional' acid-free albums and photo corners not sleeves or sticky pages; take negatives out of the pockets the processor gives you and put in mylar or melinex sleeves; and make sure you make copies of polaroids - they fade really badly in just 10 years.
Finally, it's worth remembering that CDs don't have an indefinite life either - current thought is around 25 years before the plastic starts to break down and you can't access all the data.
If anyone wants one, I have a written a fact sheet on just this subject!