I currently have two "WTB" ads in the classified ads section. What's the consensus regarding how often I should bump them?

BTW, I don't intend on selling much, if anything, here on the forum unless someone specifically asks about something I have. All my stuff will probably go on the auction site.

ETA: Searching for the same topic on APUG I've come to the conclusion that a bump every 72 hours is well-tolerated. Reasonable?