If you are counting
If the count is negative, and the game offers surrender, then you would surrender instead of splitting against the 10.
Also if the count were extremely positive (+6 or more), you would stand instead of splitting against the 10.
If you are playing European no-hole card rules, where the dealer doesn't take the hole card until after you play your hand, and you lose all your bets if he has a blackjack, then you wouldn't split 8s against the Ace.
Other than that, always split 8s.