Really interesting.

Overall I think it works well, but I have a few aspects I disagree with:

1) dT : it is an interesting factor, but I think it is wrong. Or at least it is sometimes wrong. I agree with you in some cases but in other cases it is wrong. There are watches I wear often because I love them. The satisfaction is not decreased because I wear them often. For example I took an Omega Ploprof on holiday because it is the only vintage watch I would wear surfing. I wore it every day. I ended up enjoying it even more because I wore it everyday.

Having said that, I understand you take a favourite you haven't worn for a few months out of the safety deposit box and the enjoyment is really increased.

2) SOP : I think SOP is in itself a non-linear variable. I don't agree you have a straight line simply increasing as the watch is closer to NOS. There is a huge satisfaction in wearing a really worn watch if the wear is charismatic and part of the history and appeal of the watch. So you need a more complex formula for SOP.

Then we can discuss for years what is the value of all the coefficients. I think C4 (subjective liking for the watch) is by far the biggest, followed by C1 (rarity)...

More analysis needed, but a good start Gianluca!