I don't mean this in a negative way as most of us are afflicted by it to some extent, but it's a classic case of oniomania, or shopaholism. The highs of the desire, the "hunt", and the eventual purchase are often met with disappointment and/or guilt over the expenditure, which is then followed up by the need to recapture the high again.
Most of us try to justify the purchases by assigning roles to the watches (or whatever we might collect), but that pretence falls apart when we fill those roles but still feel no satisfaction.
I wouldn't feel bad about it. If you can afford it, enjoy it. What else are we, former hunter gatherers, meant to be doing in this age?