I'm in Scotland as Rene says. Our Truck and Trailer are stored in a long garage that we rent in Boulder City. I'm so glad we have indoor storage because of the length of time we have been away.
The doors are checked and oiled every 6 months and the manager of the facility has been doing basic checks for us.
Luckily we winterise, disconnect batteries, add fuel stabiliser etc. before we come home. I am getting a bit twitchy now about what we will find when we eventually get back. But we just need to hope for the best. It's been 1.5 years now
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I know of other international travellers that use various storage facilities. There are lots of options available but as a minimum you should have a place with good security and cameras to satisfy Insurance requirements. If stored for several months you will get a discount if you notify them.
Normally we fly into Vegas, stay one night in a hotel, then go to get Truck. We connect battery then take it for a drive to ensure it is working safely. Because of the storage space we get a local boat repairer to use his forklift to move the trailer out, we hook up and go to an RV Park. We stay for a week or two to get set up, clean TT, get any servicing or repairs done, then head out for 6 months.
We stay in RV park for at least 2 weeks at the end of trip to give us time to pack, clean, sanitise etc. We get trailer and truck back into the storage facility and get a taxi to the airport.
Works very well for us.