they won't leave you stranded in the middle of the woods.  You'll know when they get too loose.  When they do you can knock a link out and run it for a while like that until you can get a new chain.  There is more friction with an o-ring chain so you lose power to the rear wheels.  It's a trade-off.....if you don't want to think about your chain for a long long time, go o-ring.  If you want cheap and don't mind keeping it adjusted, go with non.