Yes, I had this with DS, although at about 11 months I think (and also posted on here when I was sobbing in despair and bleeding from him constantly grating his teeth as he finished feeding - the scabs never completely healed cos he kept re-opening them with his teeth - nice!). With him it was teething related and lasted a about a month, or just over maybe - although most of that time I was just putting up with it.
I was really worried he was self-weaning, but apparently it is v common and DS now 14 months and happily feeding and never bites at all, even if pulling off and on cos stuff happening round him.
Advice from BF counsellor was that it can just be habit/comfort so to shout 'no' quite loudly as this shocks them into thinking about what they're doing and makes them stop. I tried this but not sure it helped.
What did help for me was changing the position of the feed for a couple of weeks so (rather than holding him across me I did a rugby hold under 1 arm) which made him latch differently and he bit much less - maybe cos less familiar? Also if he did bite then it was in a new area so far less painful! Also, sticking a finger into his mouth when I thought he was finishing feeding, to ease him off - although I usually misjudged this so had a wahhing baby.
What I did find was that if I got him off painlessly then he'd often ask to feed again immediately, latch on and then pull off with clenched teeth straight away - he obviously missed biting at the end of a feed!
Also heard that rubbing bonjela on 5 mins before a feed can ease their gums so they're less likely to want to bite.
Good luck with it though, I was in such misery thinking it was the end of my BFing DS and that I'd be left with horrible memories of BFing but now its all lovely again!