Good stuff.

Yeah, switched to dry but it's a bit late now. Still, an education.

I'm realizing that the Brompton is the AK47 of the bike world ie it's an old design, made to loose tolerances, that does what it was designed to do very well and has become iconic.

... or an Uzi if you consider the folding size ;-)

https://www.youtube.com/watch?v=au6JBGTvZ3Q

Just my 2 cents worth and bear in mind that I haven't ridden a bike regularly for years until the past few months = limited personal bike experience.
Bought a 2009 Brompton M3L second-hand in Aug and added a rear rack, Ergon grips, a Brooks Flyer and finally Kojak tyres. The Brommie was a fine bike and did the commuting bit especially well, given the compact fold, ease of rolling and the way the bag fits on the folded bike.
But I hankered after more speed and less weight... may be to compensate for the lack of fitness. So on impulse in the face of a good deal, I bought a Dahon Vector X10 and sold the Brompton (unfortunately I only have space for one bike at a time).
The X10 is more fun to ride, stiffer and faster, but less comfortable ( no rear suspension block) and less convinient to roll when folded. My X10 seems to be one of the latter batches so it has the same OCL frame joint like the Terns but NOT the same handlepost hinge.
The only bit of advice I can give is that the Vector/Verge hinges need fine-tuning and correct adjustment in the shop and after an initial break-in period = had issues with handlepost and seatpost play which was fixed by the mechanic because I didn't know any better to DIY and I didn't get back to the shop after those first few rides. No harm done but I felt slightly stupid that I didn't spot the issues earlier.

I saw the guy I know from the University with his Dahon MU SL at the station last night.... so I asked him if he ever folds the thing... his reply "only if absolutely necessary" so I said "yeah, well that is the difference between a Brompton and a Dahon... I tried not to fold the (Dahon MU SL) one I had"... he laughed.