I used to do a lot of jump seat visits years ago soon after I started flying, lots of take offs and landings, but I'm happy to sit in the back with my G&T these days. The ultimate was a 1999 Concorde jump seat trip Manchester to Paris (including mach 2.02 at 60,000 feet) on G-BOAD, push back at Manch to brakes-on at Paris (once you're tucked in behind the captain it'd be very inconvenient for the busy FE if you wanted to get out - there's not a lot of room).
On that trip, after the supersonic bit as we decelerated and descended, pax came forward for cockpit visits and almost all said "how can you remember what all these dials are for?" The supernumary captain who had given a commentrary and was supervising the cockpit visits replied at one point "I sit at home in the cupboard under the stairs and practice with the gas meter!".
And we don't allow cockpit visits in the Chipmunk. No need, really. The pax (singular) has their own cockpit.
SSD