I skied the First Chair 10s for about 40-ish days.
Durability/Longevity wise, I had no issues. Granted, these were their top end boots with metal buckles and heavier(?) plastics. These were definitely not light. A lot of complaints seem to come from their lower end offerings/boots from 5-10 years ago that use plastic buckles, which I believe FT finally ditched.
Though the 10 flex tongue felt soft for what FT rates a 120 flex, I think they're fine for all but the most aggressive skiers (also if you're cranking out carves on hard groomers all day I'd probably stick with an overlap boot). Did have one random instance where I hit an unexpected firm bump at speed and felt my lower leg and ankle 'flexing through' the tongue, as if the tongue had just lost all its stiffness/resistance for the split second of hitting the bump. Kinda scary, but that was only once.
Only other complaint was how fast the thick and soft liner packed out. Considered an aftermarket Intuition liner, but I just moved on to a Dalbello Krypton. Much better fit for my feet and stiffer fore/aft and laterally.