HU/SP from trailer expired up to one year

Hello together, I hope someone can help me here. I work in a freight forwarder and we have customers where our trailers stand for some months. There are even customers where a trailer stands for up to a year. Since it happens that the HU/SP has expired before we pick it up again. We have a list of DEKRA locations near the customers so that they can be immediately taken to the inspection center. We have heard of the commercial trailer on the direct way to I can only find things about cars and their trailers. Or does anyone know a way to bring the trailer legally to the next test facility? I really hope someone has an idea and can help me. LG is able to get to a test center if they have expired up to a year. LG has a set text or something for me, or a place where I can find it?