Is it worth it to check your paper money to see if they are collectible or valuable?

While it can be time consuming, I always check my bills to see if they are “star” bills. When bills are printed, it is not uncommon to have one in a set that is spoiled or unacceptable for circulation. It is usually cut out of the page of bills and a “star” bill is substituted as a replacement banknote.

Star bills have an asterisk(*) at the end of the serial number.

Replacement banknote — Wikipedia