You have a trailer for your boat, off-road vehicle, or motorcycle, and you want to know how to tell when to replace the tires on the trailer. This is not as easy to answer as it seems since a variety of factors come into play.
Whether you're using indoor storage to stow your trailer and vehicle, or you have it outdoors at home or elsewhere in Riverside or Orange Counties, many things can lead to premature tire wear, necessitating replacement of your trailer tires.
The first thing to remember is this: Using your trailer often is usually better than leaving it sit often. Rolling along the highway does a couple of things: It releases lubricants for the tires, and it prevents flat spots from developing, which can be the curse of stowing your vehicle in outdoor storage or indoor storage.
Another thing to consider is that, if one tire develops a flat spot, the other tires are going to have to compensate for the loss of traction and mobility. You thereby put all the tires at risk--another point to weigh. This is why some people recommend jacking up the trailer, so the wheels don't sit on the ground for long periods.
Under-inflation of the tires is also another huge problem, which you often see on 18-wheelers on the highways that blow their rubber. Most tires will lose 1-3 psi a month from seepage and usage, and the under-inflation threatens the tire's integrity. Thus you need to gauge your air pressure regularly and refill your tires accordingly (not just on trailers, but on every vehicle with tires that you own).
Another factor to consider if you're stowing your trailer and cargo outdoors--the sun will wreak havoc on your tires (and on other parts of your vehicles). This is why it's better to stow your precious investments indoors, especially in indoor storage that is cool or artificially cooled.
Bottom line, no matter what you do, you're going to have to change your trailer tires every three to five years. Remember, it's safer to be rolling than stationary, but either way, the tires, even with the treads looking fine, are working on a half-life of three to five years.