Here in Washington as and in many other places the seller has no obligation to respond within any given time frame. They have no obligation to respond at all. If the seller does not respond, the offer simply expires.
If a seller counteroffers after the contract expiration date and the counteroffer becomes the offer from seller to buyer. If the counter offer is agreeable to the buyer after the contract expiration date, you can sign the counter offer and continue on with the transaction, or make another counter offer. The counteroffer forms we use have a 2 day time frame, so you as the buyer than have 2 days to decide what you would like to do.
Sometimes if a buyer insists on too short of an acceptance timeline, the result might be detrimental to the buyer if the buyer wants serious consideration of their offer.
Strategy needs to be well considered along with practicality. If the terms of the offer are made with careful consideration, the seller will be more likely to accept!