I was with NRMA, largely because they offered lay up cover for up to 6 months when not being used, and that reduced my premium by 30%. When I first started with them (probably 7 years ago now) they were the only insurer that offer this.
I have recently moved house, and my van is now no longer in a garage, or even under cover of any description. It's still off the road, behind a locked gate, but it's not under cover.
When I phoned NRMA to change my address they then told be that their layup cover was only offered if the van was off the road, and under cover (car port, garage etc......some sort of structure) so they could no longer offer this to me. I was a bit ####ed off as that effectively increased my premium by nearly 50% from what I was paying.
I hunted around and found that there are others offering this layup cover now. I ended up changing to Lets Go Caravan Insurance, who are apparently a partnership between an insurance company (obviously) and the Caravan Industry Association of Australia. They stipulate the van needs to be off the road and behind a locked gate to qualify, but it doesn't need to be under a structure/cover. They were slightly more than the NRMA would have been had I still been eligible for their layup cover, but not a lot.