I was just wondering how long the strings usually last on Mathews bows. I have an SQ2.

2 years with no problem thats with couple thous. arrows through it . the only reason I changed it I bought a bow press.actually the cable need changed more then the string.

i have a sq2 and iam starting to see whare on the bottom of the string by the cam.

I don't have a Mathews but as a general rule I think most guys should replace their string every 1-2 years and the cable(s) at least every 2 years. I make my own and replace them every year and as a set (this way I know when both where changed). I've helped at a shop and have seen too many come in 4-5 years old that just break under the nock point. Just seems wiser to be cautious. I know the cost of string and cables holds alot of guys back but if you check around you can find good sets made for up to 1/3 what some companies are charging.

every 2-4 years

The key to string life is keeping them waxed.If you wax your string on a regular basis it will last much longer.When waxing don't be scared to use too much,and rub it in good.
On my 3D bow I usually change strings once or possibly twice a year,but this is because I may have 1000's of shots on them,not because they are worn out.
On my hunting rig I change about every 2 yrs whether needed or not.