Unless the seller is out of town, on vacation or having surgery .. then 24 hours should be just about all of it - per contract.
Any and all offers should be answered quickly .. a quick response puts the ball in motion and starts the negotiation process - and it quickly clears the air if buyer and seller are light years away in price ... anything else is a waste of time.
The time frame that is 'typical' can vary widely. PAR (Pennsylvania Association of Realtors) standard sales agreement forms have a line to fill in a deadline for seller response, (see Andee's answer- a good explanation). Many experienced agents in our area will notify all potential buyers (thru their agents) that there are multiple offers on the table, and that all are invited to make their highest and best offer by a specific date so that the seller can consider them. That notice is not required! Remember that the listing agent is working for the best interests of the seller, and they are of course trying to get the best price or terms that they can.
Ask your agent what is typical in your locale at this time. You then have to decide whether your interest in that particular property warrants waiting it out .
Hope that helps! Good luck on your house hunt.