A straightforward swap - same rail position, same door, opener replacing opener - usually runs a couple of hours once we're on site. Houses built around 1965 tend to make this the more common case in Catlin, since the garage framing was built with an opener in mind from the start.
Where it runs longer is when the door itself is original or close to it. An older one-piece door or a first-generation sectional door sometimes has a track angle or header clearance that wasn't designed around a modern opener rail, and that means extra bracket work before the opener goes up at all. We won't know which situation we're walking into until we're standing in the garage, so we quote a window, not a fixed number, when you call.
The honest limitation here: if the door itself is failing - bowed panels, a spring that's clearly on its last turns - installing a new opener on it is a short-term fix. We'll tell you that on site rather than bolt a new opener to a door that's going to need replacing within the year anyway.