When I did my ATPL training years ago, I'd say about 50% of the instructional flights involved swapping seats front/rear between students. It was really useful as the ratio of taxiing, power checks, waiting, etc. to actual aviation was better, plus you got to see much more in the way of demonstrations and other guys' good flying and/or mistakes. It also enabled two or three people to do a long cross-country to different/unfamiliar airfields with varied approach facilities and terrain/weather without burning too many hours in the process.
If plied with drink, I might tell a story about landing in a Cub in a different seat to the one used for takeoff. No way would I admit to any such practices on a public forum.
