Okay, that makes it clearer, well if it's already on collection basically it will never just "drop off your credit" you spent the money and will always owe it. Any collection agency can purchase the file and try to collect when the one that has it right now gives up.
What your thinking of is the statute of limitations, after 6 years (in most provinces) the statute expires and the collection agency can no longer sue you. The 6 years is calculated from the date of your last payment. Again, at this point they cant sue you but they can still call and send letters and generally annoy you till they give up.
You can try going to a debt consolidation company or try to settle, offer the collection agency a percentage of the total to close the file, try offering 50% and see what they say.
Student Loan Debt Consolidation and Other Options when Dealing with Student Loan Debts