First of all, the statute of limitations is not applicable to federal student loans. So if this is a federal student loan, you will not have a valid statute of limitations defense.
If the loan is a private loan, then the statute of limitations does apply. However, it doesn't begin to run from the date that you received the loan. It begins to run from the date that you went into default on the loan. Additionally, if you made any payments after the default, the statute is tolled, and the statute of limitations period begins anew. So unless there has been a period greater than six years that has went by wherein you have made no payments and the creditor has not filed a lawsuit to get a judgment and collect on the debt, you probably don't have a statute of limitations defense. In order to know for certain whether or not you have a statute of limitations defense, you should consult with a local attorney.
Best of Luck!