I took photography classes, and they told us the same thing at the college...
BUT... depending on which printer, paper, and inks you're using... you can get up to 120 years from prints done on your home printer as investigated by Wilheim Research... The main 2 out there (personal use wise) that last up to this long are Epson's & HP's products. There is some really expensive printing paper you can buy that has the fiber in it that they use in professional quality photos, that will last a bit longer(but not enough longer than the 2 types I mentioned) to pay the extra high dollar for it in my opinion.
I loved taking my photography classes at the local Art College... but the older professors can be a bit biased to newer technology... Especially when it comes to Photography. I even had professors tell me that pretty soon there weren't going to be any GOOD photographers left, since everyone could digitally manipulate everything now-a-days... How ridiculous is that??? You still have to have an eye for taking photos, even if you do play around with them, and make them artsy fartsy, so to speak.
Here's a link where you can research further.
http://www.wilhelm-research.com/
These folks are the leading in the archival preservationist industry testing, used by libraries, & museums... with very high testing standards.
HTH!