For our move about a year ago, we sold the old house and put everything in rented storage while we looked for a new house.

In our case storage was two 10 ft x 20 ft plus two 10 ft x 12 ft commercial storage sheds (we had quite a bit of "stuff").

While we had the old house, with insurance, our things in storage were covered under that policy. Of course when we sold the house, we immediately had no insurance. I made an attempt to find an insurer, and was totally denied by every insurer I contacted. An email to our State Insurance Commissioner was answered (something of a surprise) with a very official statement that unless the premises where the property is stored was owned or leased by a licensed business who is the insured the only way it could be insured was under a rider attached to a homeowner's policy (which requires you to live at a fixed address) or similarly under a "renter's policy" (which requires you to live at a fixed address). There was (is) no insurer licensed to provide any other coverage in Kansas.

Since we were living in our tiny RV, and moving from camp to camp due to "length of stay" limits, there was no insurance and no way to get any.

We've estimated the loss in the burglary at about $8,000, just barely under the income based exception that would have at least allowed an income tax deduction as a "casualty loss" for part of it.

At least in my US state, and quite probably in most of the US, the only reasonably available insurance on "personal property" is via a home-owner or renter policy, and the instant the insured home is sold, or the "rental" is vacated, you have no insurance.

Conditions may be different in other areas, but if being insured is important to you, I'd suggest verifying any coverage you have, and talking to your insurer if there's any question about coverage in your specific circumstances, especially during a "transition" such as a move.

Actual storage conditions in rented storage here can vary a lot - and can be somewhat different than advertised. Your own assessment is about all you'll have to go on. In a larger storage space, you could put your instrument in something like a "wardrobe box" and mark it "dirty laundry" in hopes that anyone who gets in may pass it up for something that looks more "marketable." In most reasonable places where you might store things, with the exception of leaking-roof-moisture or rapid temperature changes most instruments aren't really all that fragile for a short while if they're in good condition to begin with.

John