Well, they’re always good. It depends on what you’re trying to do, though.
Rings are tricky, because what’s important to me in a ring is the cooldown score, so I don’t really want to dilute my cooldown by refining on other perks. Rings get slightly higher refined perks than other items, though, but in pure numbers, they’re going to be smaller than a 2 perk bronze ring.
But refining a perk onto another item that can’t naturally get it, like cooldown on shields or armor, or rare perks, etc… I think that’s a great use of refining and if you have the resources, it’s worth doing at any level. I don’t usually recommend that players wait until they hit a certain level before they start forging/refining. The exception would be if you have a bunch of major upgrades ready to go and you know that you’ll be levelling up several levels quickly. Then it could be smart to wait until your level is more stable.