Buying a new alpine/tower rope

I have a nice 60m Sterling 9.8 for sport routes, and for multipitch a 70m 9.8 that's getting on in years, might need to be retired in another year. I also have a static 8.3 60m for double rope raps.

I'm deciding on a new rope I'd use for Utah desert towers, Elephant's Perch, Devil's Tower, Lone Peak, Red Rocks. To mix up with what I currently have, I'm eyeing the 80m 9.2 Sterling Bicolor Fusion Nano. Thoughts on the length and diameter? I could just wait another year and replace the 70m if 80m is excessive. Also don't really mind 9.8mm.

I've got the Mammut Serenity 8.9 (70M) as an alpine route and I really like it. I haven't used it on any sandstone, but I've used it on a great many rock and mixed alpine climbs from NH to CO to the Tetons and it's yet to show any wear. I highly recommend it.