Nightfall said:Mister Karin's Dad,
Thanks for that update. I just remember we didn't bother with it when the wizard wore it last. At least not that I recall off hand...
It's important to the OP's question in that a Ring of Sustenance is not as great of an item unless it is house ruled to allow regaining of spells after 2 hours. With such a house rule, the 8 hour window of no new spells drops to 2 hours and for encounter purposes, that's a big drop (hence, giving the ring a high utility for the cheap cost).
As written, the Ring gives the Wizard the benefit of being awake more often, but at the cost of requiring even more rest if a combat occurs. With the house rule, this would not be an issue.