There was a similar arrangement when Lloyd Humphries was at Weston last season, it seems like a good deal. I guess Duffus will still do most of his training with us and is available to play if things don't work out at Hereford but with them having two games most weeks and him doing well so far I'd be surprised if he plays again for us before the loan spell is over.
Hereford aren't playing at a high level but I can't see any harm in Duffus going there. Playing competitive games (including an FA Cup tie at Fleetwood) in front of decent crowds is surely better than playing a handful of under-23 games in a wind-blasted athletics stadium in front of TOBW, Cyncoed Slumdog and the girlfriend of one of the subs.