The longest distance (so far) that I have towed my ~900# teardrop is from the SF Bay Area to Yosemite and back. Around 4+ hours each way. That said, the road into and out of Yosemite Valley is very steep with many switchbacks. My 2.5 CVT performed admirably and I would niot hesitate to do it again...or over the Sierras for that matter. The paddle shifters worked great especially on the downhill switchbacks. :29:
When I purchased my 2012 Outback I went with the 3.6 H6 so I would get a real transmission. My thinking was if the CVT could not handle the 3.6 H6 then it probably could not handle any kind of a trailer even behind the 2.5.
I get 20 mpg towing a 2200 lb trailer with my 3.6. I doubt a 2.5 would get much better mpg.