45-60 days is the most common, and extensions for financing should be expected. I recommend that Buyers include a due diligence timeline in their LOI, attach a checklist of the items they need to perform DD, and make it clear that the timeline starts when all items have been received. The timeline should include regular meetings between Buyer and Seller to cover items that need to be discussed in person. I have in the past advised a Seller to pull out of a deal when the Buyer-proposed timeline was ignored, as it was clear that my Seller was not top-of-mind for the Buyer.

We almost exclusively sit inredacteddays. Why? Because our DD and review takes 2-5 days... maybe 7 after all docs are in. Buts seller's takeredacteddays to deliver docs needed to do DD (sometimes 2x that timeline). Then lenders also takeredacteddays to credit preview before a term sheet assuming no major questions or new docs to be provided you don't already have - never mind get to commitment letter. By the time you wait out in most cases 100 days of exclusivity goes up in flames waiting on the seller or lender. Assume you're using lending in the process that is.