Others have covered the topic well.

I recently bought a house and used a buying agent. The deadline I wrote on my offer was 10pm the same day on the advice of this agent. It wasn't my idea. I assume the agents are trying to get to a decision really quickly so that they can either collect commission or stop wasting time.

However, I also appreciated that I didn't have the possibility of being tied to an offer for a long period of time if the seller needed to hum and haw. I didn't want the seller to sit on my offer and see if other offers would come in. Also, other houses were on the market that were suitable to me. If I didn't get the one I was looking for, I needed to know right away so that I could move to my 2nd choice. I knew there were people looking at my second choice, so I wanted to move fast before they had a chance to put in offers.

Since you need to have input from others, put a condition in your counter offer. Buyers have conditions. I expect you as the seller could do it as well (subject to bank approval if the house was collateral for a loan, etc). But, if I were buying, I'd be likely to walk away if the condition was for too long. My assumption is you already had the majority of the variables decided before listing the place. The only reason for needing advice after listing should be because the offer had something unusual in it. Let's say, they asked you to provide a private mortgage or something.

BTW, in my case, the counteroffer also had a short deadline. I had to reply back by the evening of the 2nd day from my first offer.