Great cars and durable. They're highly underrated for overlanding as are XC90s. We have enjoyed our 2010 XC90 so much that 3 yrs ago we got a second one - 2017 XC90 T8 (we've done factory delivery for our Volvos).
The nicer thing about an XC70 vs. XC90 is there seem to be far more options for building it up for overlanding. I've seen a couple of cool builds locally that are pretty rad. The only downside for us with an XC70 is space and flexibility (we're a family of 5). It's why we're partial to the XC90. Actually our first Volvo was a V40 which served us well until 2 yrs ago. We sold it with 200k, our 2010 XC90 has 148k and our newer X90 has 26k. Take care of them and they will last. Our 2010 is still going strong.
We've gone way off the beaten path with our XC90s and they're basically stock. The mods I've done to our 2010 have been adding AT tires, Volvo's Aux Light kit to mount VisionX light canons, HAM radio install, Thule roof basket to carry 2 full size spares and 2 jerry cans, or any combination of them and other gear (was great for our trip to YK, AK, and NWT). We also have 2 sets of wheels, 1 set for AT overland/road tires and 2nd set of studded winter (we tow a lot with ours all year round with most towing miles being winter through heavy snow and ice).
We've tackled sand dunes, mud, wet thick clay, semi thawed permafrost, slate, rocky trails (with careful tire placement), deep snow, desert (powdery sand like flour), high altitude (>10k feet) and while towing and continue to enjoy them.