If your route has regularly spaced fuel stations, it's doable. If you travel when they may be closed, it could be very problematic. I'm not a fan of carrying gas cans in a vehicle. Some do it.
Comfort is very much an individual thing. When I've driven mine near its full range (a BEV), near the end, I was not very comfortable, so even if I'd opted for the REx version, I would not want to drive it for 6-7 hours or more, even with stopping regularly to refuel. As I use mine, comfort is fine, as I use it for running around town, and rarely more than 30-miles in any one stretch. If your trips are in the winter, keep in mind that all of your heat is via the batteries, whether you heat the seats, the cabin, mirrors, or keep enough going to keep the windshield clear...in some weather, that can make a significant impact on your range. That's still true with the BEV, but unless it's really frigid, the heat pump is more efficient at producing heat.
If you were buying new, and your normal day was way below the pure battery range, the cost of adding the REx and the additional maintenance required, might just pay to rent a bigger hybrid or ICE vehicle for an annual trip. Then, no issue about being sure you'd get there.
2014 i3 BEV, 2021 X5 45e
(The i3 will be sold soon, <17K-miles, interested?)