As with any insurance company or cell phone company if you send them a copy of your orders putting you on Active Duty (BCT, Scools, Deployment overseas, etc) you can usually get a military hold/suspension put on your account if the vehicle is going to be parked/cell phone not used. Then when you're back and able to use it again just call them and they'll restart payments.
The account will stay active, and they'll still cover the vehicle for theft or damages, you just won't have to pay them during that time. Just keep in mind if you get into an accident while driving without telling them you're driving again then they can refuse to pay for any of the bills.
I can personally tell you Sprint/Nextel, Verizon, Dairyland, The Hartford, USAA, Geico, and any Insurance through Harley Davidson will do a hold.
I've never heard anything bad about USAA, still never used them though. Never had a use to switch companies yet.