How late is too late to cash a gift check?

I just found a check from my grandparents that was sent as a gift for my birthday in April. I didn’t meet them until I was 21 and have not kept in touch with them at all. I am somewhat in touch with my father, but not a lot. They almost always send a check to my husband, daughter and me for Christmas and our birthdays.

Now I wonder if I have upset them by not cashing it. I am even more concerned that cashing it now would mess up their banking. What would you do? BTW, I did write a thank you note immediately after I received it.

I keep thinking about the Seinfeld episode where Jerry didn’t cash his nana’s checks, but at least this is just one for $20.