You should check...some of them cap out. My wife had one that her aunt bought for her in 1965.
Found it in a box of savings bonds in her room when she passed. A shoe box full of savings bands—can you imagine? It took three days for the local branch to go through them all.
I am watching that. The Treasury has a website that yo can enter your bond numbers and they give you the status as of the date you enter. They all have room to run.