We've been living in an RV (6x6 truck actually) for 14 years, if we can find a water source to camp by we should be able to get by for at least 3 months without resupply, in theory pretty much indefinitely if I was into obtaining protein from the land.
A month here.
Six weeks here.
Two months here, only left because the river dried up
These places are fairly exposed but of course we weren't bugging out. But this place
Was well off the beaten track and teaming with wildlife and cattle. With a gun I reckon you could live there for a heck of a long time and nobody would know or care. We stayed 4 weeks because there was no internet connection and I needed a fix
As a BOV I think they are great but it depends on the situation, for natural disasters, yep, for long-term TEOTWAWKI not so much because of the fuel issues and a vehicle of any kind (let alone a well provisioned RV) will be a trouble magnet. That said if you have a BOL with no facilities you can just move everything you own out there and sit tight. Maybe erect a shed to store more preps but no need to spend a fortune on the BOL facilities. If you are living in it anyway it's just a matter of turning the key and going, nothing to pack.
Emptying sewage and grey water is a no-brainer. Grey water just runs out a hose, maybe run it a few yards from the RV or carry away in buckets every few days. Sewerage, take the canister into the bush a 100 yards or so and dump it. I've been stationary in my current location for 2 years now, I found a hollow tree stump and have been dumping the loo into that for all that time, you would hardly notice even if I pointed it out.
Solar is just a given, I don't understand why everyone worries about refrigeration etc, we have 4 fridges, 2 of which are on all the time. We use computers, use all the normal power tools, I even occasionally do some MIG welding etc etc, there's very little difference between living on solar and on the mains although of course you tend to be more frugal with your power usage. Even my little Suzuki has solar and a fridge. Naturally the climate makes a difference, I live in a very sunny country.
Note the solar panels on the truck roof (we have a lot more capacity these days), and the Suzuki's panel is out as well because we were using the fridge in the car at the time.
So it's certainly a good way to go IMO with the already-mentioned caveats about storage etc. But for long term it depends on your ability to live off the land.