CVT's are only durable behind smaller engines. Mfgrs are working on torque capacity but most require a ton of torque management written into the software to protect them.
Regular slushboxes do the same, but can easily handle 500 foot pounds and more while towing and such.
According to the driveline engineer I know a CVT also makes the engines easier to calibrate for mileage due to the steady rpm...
Pretty much.
Also from my school project back then with CVT, the biggest problem is they are constantly gripping and releasing between the belt/pulley or toroidal/disk instead of grip and stay of the clutch pack during cruise. When combined with the constant ratio changing, the amount of wear on the frictional surfaces on CVT are much much higher than on clutch packs. If you ever loses some pressure it would slip and almost immediately wear out a huge chunk of frictional surfaces, and likely kill the unit immediately.
Comparing to 3 speed auto CVT the fuel economy difference is huge, 4 speed is a good amount, 5 and 6 speed it is negligible, especially with variable valve timing that brings you wide power bands.
Dual electric motor IVTs like the ones in Prius are very good, so good that they have almost nothing to wear out on.