A quote reflects a site visit, or a phone description of one. Each access condition in the room can change the time the job takes. Time is the labor line, and the labor line is one of the parts of a quote that moves most with the house, not with the equipment.
Look for these access conditions on the quote. Is the unit going into an attic, a crawl space, or a closet? Will the crew need to pass through a narrow door, a tight stair, or a long hallway? Does the outdoor unit sit at ground level or on a roof? How far is the run from the panel, and how far is the run for the condensate line? Is the existing duct in good shape, or will it need work before the new unit can connect to it?
Check whether the quote names each condition, or whether it says only that the site was visited. A named condition can be discussed. An unnamed one is a question you still need to ask.
Ask what the quote assumed. Did the installer measure the closet door against the cabinet? Did the visit include a look at the crawl space or only the access hatch? Was the outdoor unit location confirmed on paper, or only described on the phone?
Note any exclusions the quote lists under labor. A line that says a certain access item is not included is not the same as a line that says the item is included at no added time. Read both carefully.
For central cooling, the Central Air Conditioner page explains when a system is in its planning window. That window tells you how long the equipment is likely to serve. It does not tell you the labor time, so keep the access notes and the planning date in separate columns of your folder.