There is no time limit on how long it can take a check to clear. I have seen checks come back to my bank (unpaid) 3 weeks after the deposit, this is not terribly uncommon.
YES, you are responsible. You claimed responsibility for that check the day you deposited it into your account. If it comes back (today, tomorrow, or in a month or year) the amount will be debited from your account.
To gain any kind of assurance that the check has cleared the bank (assuming it is a bank check) your best bet is to call the bank it was drawn off of and find out its status.
Probably not what you wanted to hear, but at least now you're aware.
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...lemony fresh victory is mine!