In November 2014 I bought a 2011 Nissan Quest with a cvt and 48k miles.
I did a siphon and fill when we first got it. Got about 4 quarts out and replaced with genuine Nissan NS2 fluid.
Did another siphon and fill November 2015 at about 57-58k also with OEM fluid.
The first change, the fluid looked dark but not terrible. The 2nd change the fluid looked slightly dark, but not as bad as the 1st.
The fluid on the stick after the 2nd change looks like new.
I may just do a siphon and fill on this unit every year.
I may switch to Amsoil CVT fluid for the next service as it will be past the 60k power train warranty.
I'm an Amsoil dealer so the fluid costs considerably less than the dealer fluid.