I worry about some of you. I have the trailer that is shown in the picture. It is dead easy to attach and detach. Even every day. Even two or more times in the same day! You don't use a trailer every day, but say you did, then... even better, you don't ever detach it. Simple.
When I lock my bike with the trailer attached, I run the cable lock through the trailer tongue and the rear section of my bike. The front wheels are not quick release. If I am in a high crime area I use a U-lock on the bike and use the cable lock to lock the trailer to the rear section of the bike. If I had it to do over again (are you listening o.p.) I would probably get the Xtracycle kit that is pictured below my trailer and call it good. FWIW.