On an offer to buy with a contingency to sell a current home, are we seeing 60 -90 day closing dates

Since events expand to fill the time available, I would usually choose a 45 day close, then enter a note in my calendar to circulate an Amendment to extend the date a few days before each deadline.  Then enter another note, etc.

If representing the seller:
I would also suggest the use of a 12 hour right of review since few people really need 24 or 48 or 72 hours to ponder this, and they could use the longer periods to drive away new buyers.

Of course, do all the other work needed to protect your client such as making sure the contingent buyer actually has their house for sale.

By the way, most professional sellers absolutely refuse to accept contingent-on-sale offers because they can work against the seller client an can create serious domino effects.  Take this for what it is.

On my own house I supposed I'd take a contingent-on-sale offer if it was good and if also I was a little desperate.