I've been trying to convince the First Mate that it would be wise to replace our ten year old Mini with a nine year old Cayman. No luck so far...
I imagine your First Mate is just as all seeing as was mine. Looking at this equation coldly, from the outside, where it is often that bit cooler if one discounts artificial heat or freshness within, I'd say that her reluctance is understandable. Looking at the Cayman with male admiration, I'd say it's a far more delightful object than the 911 which should really be retired and allowed to fade into the questionable, hedge-ploughing glories of memory.
However, I believe your FM probably mirrors my own reasons for not buying some old(er) exotica: replacement parts and the specialist labour involved are geared to suit the deep pockets of the new buyer. If I were able to afford that, then I'd opt for the whole thing, new. I have no idea where you'd have to live to get reasonable insurance: after we left the UK I bought a year-old Fiat 127 (in 1982) to keep there for use during our returns (I was still working) and the only permanent address available to me was my mother's up in Perthshire. She left there, and as my son, living in Glasgow, also used the car, I had to transfer the address to his, city-centre: it was going to run over a grand (pounds!) so I just told him sorry, and sold the car back to the dealership. (This was owned by our yachtie friends here...)
A new Mini would be very nice, too! However, if your Miss Cooper has no rust problems, I'd run her into the ground and then see what's available on the market at that point. The smell of new upholstery fades within months... and with it the pride in the new purchase, but the security of the guarantee is still firmly alive and on paper somewhere!