Funny, I have been looking at Tern too (as well as Riese & Müller). Do you use it in the city as well? Which one do you have? How often do you really fold it up?
Alternatively, I've got a Brompton and I love the thing to bits. It folds in 30 seconds or less, small enough to put under a table at a coffee shop. They're incredibly well-built, and parts are easy to find. You can even get electric conversion kits.
I had a Brompton for about two years but did not like how it felt riding it to be honest. The rather weird six gear box thing and lack of disc brakes (especially in rain and winter) was also not that amazing