Now the weather has got above 15 degrees C, my range in EcoPro+ is showing just over 80 on battery plus just over 80 from the REX. Take off a little bit for the US tank size and "upto" 150 miles is certainly achievable. If you drive in Comfort with the heating on and do 75 on the motorway you'll find that reduced by at least 10 miles for each power source. So only 130ish.
Last Thursday I managed over 360 miles on a commute + long drive. Started with a full charge at home. Ran the battery down to 30% on my long 120 mile commute, switched on the REX. Got back home charged to 100% on a 7kW unit whilst getting packed, having dinner and snooze. Drove 80 miles (15 on REX to keep a bit of charge for faster sections. Got to a failed rapid, 5 more miles got a succuessful rapid charge at BMW mini plant in Oxford which is free Ate our KFC whilst we waited and was at 75% by the time we got going. The another 20 miles to stop for a full top up to 80%, but after taking my 1yr old daughter for a leg stretch got back to find it 93%. Then the final 80 miles to destination (with about 15 on REX) and trickled charged at mum and dads overnight. In my old ICE I'd have had sto stop at 290 miles for fuel. So really the only extra stop was 1 failed rapid and 1 at mini. IF I'd stuck to my original plan I'd have only made 1 rapid stop and refuelled at the same time as i stuck a 10 litre fuel can in the frunk. Save queueing again for fuel as it can be done whilst charging (if you ignore the potential dangers of 50kW going in one end and flammable liquid giving off gases at the other).
The key thing to learn - is you really need to get your REXs coded so you can enable the REX anytime you want. It makes it a totally different car and you can use it like an ICE. Run the battery down first to about 12.5%. Then use the REX till you get to a rapid. Add fuel, electrons and fill belly and thermal coffee cup and you are good for another 150 miles, and can either use another rapid - or splash the fuel from a jerry can. Or both. That's 300 miles with 1 stop. 450 with 2. That's not much of a compromise. If you want to go fast (70+mph) - switch on the REX at 50% and the SOC will keep dropping - so you are using fuel and battery, when you get fed up of the REX revving like mad as it's got 10% below the set point, turn it off and on again if it's above 12.5%. If not slow down to 65mph for 5 miles to let it catch up. Good idea if you aren't sure if the rapid you are aproaching will be working. That 12.5% will mean you get plenty of chance the see the charge dropping before you get anywhere near the slow down point. I've driven my REX US style once (letting in come on automatically) just to see what happens at high speed. Nothing. But then we don't have mountains and most roads you get stuck at under 70 due to traiffic. So the REX catches up eventually.
Fuel is everywhere. Carry a 20 meter/60 foot 15 amp extension lead to plug your portable EVSE into - and so is electricity.