I did cheat and take the bus back to Falmouth, though even with that according to my phone's step counter I walked over 10 miles! I know I've said this before, but 10 miles really doesn't seem all that far anymore. Yesterday I walked from the holiday cottage into Falmouth, pottered around the high street, and wandered up to Wodehouse Terrace and back. I... can't come up with a solid mental feeling for what sort of distance that was, but none of it felt like being any real distance. It's all what I'd consider to be local.
According to my phone that was probably a mile and half to get to the centre, another 3 miles around town, and a mile and half to get back.
Anyway, Trebah gardens. Since I was last here (13 years ago!) they've built a new visitor centre with restaurant, neatened up a few things here and there, but not all that much seems to have changed. They've still got the koi pool, the giant rhubarb (unfortunately not sprouted yet this year), the plaques with the time trail, and the private beach with the funny narrow stone steps to it (turns out this goes over the coast path). It's still well worth a visit.
Interesting bit of trivial: the US 29th Infantry Division embarked from the beach at Trebah as part of the D-Day landings (to land on Omaha Beach, in this case). There's a memorial stone at the bottom of the gardens, and they hold a remembrance service there each year.