I've seen the board have 4 Aces before... I was sitting there with pocket Kings, and initially I was wondering if the remaining Ace was going to take all my chips... then I saw the last one and knew I was OK... I think I turned out to be against pocket Jacks. I think that's the only time I've seen 4 of a kind on the board so far.
It doesn't really qualify as a bad beat if you're all-in before the flop - you were only a marginal favourite with 5's. If someone is going all-in every hand then you have to pick something better than 5's to play with - AK, AQ, even AJ or AT if it's literally every hand, or the real premium pocket pairs, otherwise you're condemning yourself to a coin flip, generally with all your chips on the line rather than all his. Even with AK you'll go out more often than you'd like - only AA, KK or QQ would be likely to be solid favourites, but at least you'd have a noticeably better than even money chance with 2 overcards to his rather than an underpair.
Welcome to the forum, though.