I just leave them sitting on my vape gear table. They're tasty right out of the mailbox but better after they age a bit more. It's why I've started buying bigger bottles. You can detect a change by the time you reach the bottom of a 100 mL bottle.
In the case of blending together Boba's and Kentucky Vanilla, I like to let the blend meld for 2-3 days. There is definitely an improvement after a few days.
Thank you MaxUT