About 25 years of owning nothing but Martin Logans and Apogees.
Quads are well protected, far more so than Martin Logans, but they do lose performance over time. Basically material degeneration. Loss of tension, diaphragm coating failure, ribbon adhesive failure, clamp damping material failure etc etc.
I went through about 5 sets of ML panels in 17 years.
All speakers fail eventually. Planars are far less reliable than dynamic speakers. I did a survey on Martin Logans and the failure rate is really high.
I have a pair of Apogee Caliper Signatures I purchased in 1991, still going strong.
The only work any Apogee has needed that I know of is new foam, and, if you so desire, new Graz ribbons. I had my Caliper Signatures redone at the 18 year mark in 2009 and there have not fallen in quality since, now at the ten year mark since their rebuild.
I can't count how many people I know who have needed new cone drivers in their speakers over the same time interval of ownership, particularly Infinitys of the same era which have all needed new drivers due to rotting surrounds.
If one of the Botticelli owners could contact me, I'd appreciate it - I'd really like to know how they're getting on and I have a few questions the general audience here might not care about.
Personally I walked out of RMAF willing to pick up a pair as they had
all of the Apogee magic and none of their shortcomings, and that includes dynamics.
Compare to the Analysis Audio Omegas which always looked like Apogees but never captured the magic the Apogees did, always instead sounding dull and lifeless.
Of all the speakers I have heard over my life, and there have been thousands including the Wilson Alexandria XLFs with Thor's Hammers, the single best pair of speakers I've ever heard have been a pair of rehabbed Apogee Full Ranges at the home of Apogee restorer Rich Murry.
I have never heard better sound before, or since.