Here in Michigan we have permanent trailer plates that are good for as long as you own it. They do cost more ( I think mine were around 200.00) and are not transferable. I know lots of people buy one for there cheapest trailer and just use it on all of their other ones. I have had a utility trailer for 15 years with the same plate but if you upgrade RV's a lot it does get expensive. No tags on them but I could see the theft potential. I think just a Torx head screw would work for most thief's.
Ed & Brenda
2015 Coachman Freedom Express
Liberty Edition 297RLDS
2013 Silverado 1500 4x4 6.2L Max Tow