In the Dec 07 Zymurgy Charlie Papazian reviewed bottles of homebrew going back to the first AHC competition that he had stored, and none of them went bad, some had not held up but most of them he felt were awesome...We're talking over 20 years worth of beers.
Since nothing pathogenic can grow in beer, there's no worry needed about getting sick from them. All that can happen is that they may not have held up over time.
This is a great thread about one of our guys tasting 4-5 years of his stored brew.
https://www.homebrewtalk.com/f14/revisiting-my-classics-160672/
Beer's like wine, a lot of them improve with age....That's why stone has "vertical epic" with vintage, and people have vertical tasting parties...Our beer is really no different, it's not something "less than." Or isn't "real beer" it really is no different, just becuse you make it at home. High grav beers can last a long time...even lower or medium grav ones can, though they will loose some of their "oomph" over time. For example a really hoppy IPA might end up being a pretty tasty pale ale in a year or so. Still drinkable, still good, but not the same.
I'm looking at brewing a biiiiiiiig barleywine in a few weeks, to lay up til my 50th birthday. I turn 45 on friday, so I thought this would be a great thing to do.