I don't think there is an expiration. If there is, I would assume at least 6 months until you'd have to get re-issued a fresh check.
I've held on the checks for longer than 3 months and I didn't have any problems cashing it other than the bank thinking I was a liar to be a google employee.
That depends on the bank's policy. Say in Hong Kong, I need to clear the bank check within 6 months, or it will become a trash.
google has money to pay for the check no matter when you deposit it. however, some bank will not accept a check if it more than 3 months or 6 months old, depending on their policy. but you are 100% safe if you deposit it within 3 months. i myself once deposited a almost 2 year old check (forgot to deposit it and found it in my old files) and it was cashed.
you shall follow your check date void after 180 days you also need to know how long does your bank take to cash the check. if your check expired - earnings credited may back to your account in 1~3 months after the check void.
I would take a rough guess that the cheques dont expire but with different banks, laws and countries id advise maybe dont wait longer than 6 months. Frankly id want to get my cheque cashed straight away.