Cookies don't last forever, certainly not across different browsers. It's why you keep having to accept GDPR policies over and over.

The reason why you have to decline tracking is because they want to wear you down.

My point is that you get this even if you try to do it correctly. The best you are ever going to get with cookies or local storage, even with the best intentions, is "ask me again later".

Cookies don't stick around forever.