What is the shelf life of canned tomatoes?

Home canned goods can be safely kept until the lid starts to rust or the seal is broken, but really should be used before the next harvest. Commercially canned stuff usually carries a best-by date. I wouldn't use it much past 6 months later.

Canned goods, if properly canned, can last nearly indefinitely. There are reports of people opening 100 year old cans and the food tasted the same as stuff canned a few weeks ago. The key is effective canning. Assuming there are no dents, cracks, rust, or leaks, a canned product can last a very long time. A properly packaged can effectively prevents the chemical processes that break down food. I would not worry about them going bad anytime soon.

As long as the tins are in good condition, properly stored and handled they will last months if not years.