I am in my late 50's, 2 1/2 years out from mandatory retirement. I do what I am asked to do. I was offered an option to stay put, but go oversees without my Wife for 13 months, but I don't want to leave my Wife alone. She is awesome, smart, nice, and beautiful. But she doesn't do some things well like drive and park at the airport, etc.You must love your employer, so you are going to continue to relocate. I also see that you have a lot of stuff that you don't want to part with. I get it. I guess you'll have to eat some of the costs yourself. I guess you could buy a couple of used trailers and then sell them when you are done hoping to not lose any money by doing so.
Maybe another option is to post ads where you are moving to telling people you will bring a trailer from where you are moving from to their location with the condition you'll use it for your cross country move. That may be an option or a total pain in the neck.
My next move- I will be dumping most of "my" stuff. I have a ton of tools, auto parts, a mini hardware store in my garage. Some neighbors love me. Like my last neighbor who needed to fix the broken base on his heavy patio umbrella. He came over, asked for help, did a quick inspection. Went into one of my parts piles and pulled out a Butt Joint Exhaust Seal Band Clamp (see pic) that had moved around the country with me for the past 20 plus years. Five minutes later, his umbrella functioned like new. Maybe I am a moderate hoarder of tools and hardware?