It does depend on the extension (.com / .biz / .info) but may take up to 48 hours. And that's a registrar-independent value. Most registrars update "their" DNS's every several minutes.. it just takes time to get that info "propagated" around the world... L.
The only factor the registrar controls is how soon they submit all DNS changes to the Registry of that domain name extension. Beyond that, they really have no say. The VeriSign COM NET Registry says they'll submit the DNS change at least 5 minutes after receipt from the sponsoring registrar in question. After that, it's anyone's guess. No single party controls all the factors involved in how soon a domain name is going to resolve to its intended destination.
my .com domains on my godaddy reseller site usually show up within 24 hours.. the odd time it may take a little longer but usually even it shows up within a days time