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.
How long before a check becomes void? A: According to RealSimple, banks are not required to honor personal checks that are more than six months old. Checks older than six months are considered stale dated, and it is up to the bank whether or not to honor them.