The below goes for both my wife and myself, as we travel together.:

1. We take about 8-10 F flights for leisure per year.

2. 6-8 of them paid

3. None - don't fly longhaul for biz.

4. About 80% is paid for. But often prebooked when they have offers out. We've taken several full fare trips though, where we needed the flexibility.

This is probably the average over the past 12-13 years since we started flying F.