Serious question, my grandparents, God rest their souls, began buying me a 10-year Treasury note on my birthday about 15 years ago. This lasted about 10 years.

My question is, does this insane drop in the t-bill rates effect my t-bills from 5-10 years ago? Should I cash these notes out now since the interest is going to be so low, or were my rates locked in when the t-bills were bought?

Any advice would be appreciated and you will be personally thanked.