Sure, agreed, but let's say the buyer doesn't accept on the spot in mere seconds. So no agreement is made on how long the counter is good for. Buyer goes home to check his finances. He comes back an hour later and says, "done deal!"
The seller seems firmly within their rights to say, "Sorry, my counteroffer was good only for 15 minutes."
This might sound silly but market conditions change in minutes and events happen like earthquakes or 9/11. In the absence of an agreed term of expiration I see no reason why a counter is good for any longer than the seller feels like it. Though with written or implied terms it would be totally different (see real estate contract offers for examples).
Am I missing something?
