Exactly from the time you start until the time you finish. I'm not trying to be smart, but there are so many variables in moving snow that it's hard to say. It all depends on the type of snow, how deep it is, how packed it is, and how uniform the surface under it is. Others may be able to pin this down better, but I would think a couple of hours anyway. It could be less if you just do a couple of passes out, and back. I blow two+ cars wide so that makes a big difference too.
Like ChuckinNH said there are alot of variables in play that makes it hard to determine how long it will take.
Are you talking about a front blower or rear? Front blower you are limited to a 47in blower. The rear I think you can get away with something from 48 - 60in.
You told us that your drive is 1500ft long but how wide is it? Do you have a turn around? 2 or more door garage and parking area?
I would think for an average snowfall 6" or less just the 1500ft maybe 2 to 4 passes around 20 minutes. But if you add a turnaround large parking area and such I think it can take you up to and hour or more.
Also if you can update your information on where you are located it can help us alot on what kind of snowfall you get.
I have a similar driveway-up and downhill and curvy and about the same length with a circle drive at the end. Two days ago I did mine and two neighbors (each with a similar drive) in two hours. We had just over three inches of snow. I have a 4110 with a 47" front mounted blower. HTH
I doubt it. You are perfectly right in your assessment, save for a very small area and unless one uses a massively oversize machine for the job there is no reliable way of predicting exactly how long it will take to clear snow from a given surface even if you've done it for a decade. That's the reason why snow removal contracts always have a "tardiness provision" related to weather/snow/surface conditions.
My drive way is paved 450 feet by 10 feet wide and just doing that portion only takes me 5-10 minutes tops depending on the amount of snow. By the garages is what take more time, typically 10 more minutes for that area. Overall 20 minutes for the whole thing with 6-12 inches of snow. I use a 2210 with a 47' blower. However, if it is a real wet/heavy snow I will slow it down a bit and it probably takes an additional 1o minutes because of the speed. I did plowing initially, but the drive way kept shrinking as the tractor isn't heavy enough to force the snow further out. I also have pines lining the drive way so I was limited how far I could push the snow. Since switching to the blower I can get the job done faster and I don't have to keep dealing with the snow as it piles up.