How long does it usually take for a skeleton watch to lose most of its value?

Most of it happens in the first 12-18 months,honestly. The moment you walk out of the store, you're down 20-30% on a lot of mid-range skeleton pieces. After that it flattens out more than people expect.

Depends heavily on brand. A skeleton from a fashion-adjacent label can lose 70% in a year. Something like an Oris or Frederique Constant skeleton will hold better, maybe 30-40% over two years. The finishing and movement matter more than the fact that it's skeletonized.

This is why I only buy used skeleton watches. Let someone else eat that first hit.

I'd push back a little on the idea that it 'flattens out.' Skeleton watches can be harder to move on the secondary market because the buyer pool is smaller. So you might see asking prices stabilize but actual sale prices keep drifting down for three or four years. It's not always a clean curve.

Agreed with the above about liquidity. I had a skeleton chrono that sat for months at what seemed like a fair price. Eventually sold it at around 45% of what I paid after two years. Not terrible but not quick either.

What brands are you actually considering? That would change the answer a lot.

Also worth checking completed sales rather than active listings. A lot of skeleton watches are listed high and never sell, which makes depreciation look gentler than it is.

Raymond Weil skeleton pieces depreciate pretty steadily from what I've seen. Two years is probably where most of the damage is done.

Maurice Lacroix is a bit better on resale than people give it credit for, but the skeleton models still aren't collector favorites. I'd expect similar timing.