The main benefit of not retiring is you don't have to spend half your time with a sub par char. The bonus from 30-35 is pretty small, but the fact you don't ever have a crappy char makes it worth it for me. I would say the benefit of not having a poop char for half your time also outweighs having lots of looms, but thats just my opinion. I would recommend getting at least a few masterworks before stopping retiring though if you intend to go 34+
You don't have to retire at 31 though, you can go to 32 or even 33 and get a similar amount of gold for your time. Just you won't get the bonus XP for gens as fast as retiring at 31 (as they are delayed until 32/33)