Software Engineering is an interesting mix of practice and theory. On the theory side, you should make a habit of browsing / googling for things that are a good intersection of interesting to you and novel. Be forewarned, some of the common places to get information (like stackOverflow) can be very intimidating.
The standard expiration date for most checks is 180 days (six months) and personal checks are included in this policy. In the United States, banks are privately owned and not government operated so banks do have the right to refuse your deposit if there happens to be any suspicion of the item's negotiability.
Full Answer. Some checks, such as payroll checks, have a specific expiration date. In this case, how long the check is valid is written on the front of the check. For instance, a check that says only valid for 90 days from the date issued will expire 90 days from the date on the check. In some cases, the issuer of the check will send a new check at the recipient's request, but they are not required to do so.