I will go with your bootfitter and don't think they are necessarily wrong; and 15days is probably correct as a cross over point. A lot of that weight is the initial dialing it in which may take 10 skidays for you to dial it in and make adjustments. If your bootfitter isn't on mountain that you can't just go midday or between ski days; that could take half a season away with you skiing in pain. If you even look in this thread there are a good number of folks still having with the soft tongue and needing to add cork here and there. There is something also to be said about the booting up hassle which is also harder the less you get used to it.
The question is: if they are saying they don't recommend zipfits for you...the followup is that means they have another better recommendation for you. So what is the alternative option here for your usage pattern?
I think you can get equally good results like a foam injection (like surefoot) or other aftermarket liner if that's what they are thinking. If chosen and setup properly can be ready to ski on day 1 with less breakin issues; and less chance that you need to go back for adjustments, and ostensibly no soft tongue issues
Although these will pack out faster than the zipfits and there are reports of decreasing quality, these aftermarket options still should be very high performing for 100days; and good performing or fixed up to be good for another 100days. So that's puts this setup in the 8-16 seasons range. You will probably will be ready for the next thing anyway or global warming or corporate greed will have changed skiing.
