Hi,
You got a great deal. Where can I get that kind of deal?
Chances are that the tire pressure was checked at least once a week, and they are well taken care of, except that they might have been running 80 - 90 MPH sometimes. (depending on where you live, and if the freeways are in good shape). Intercity, they might have never gone over 55 MPH. But some rural areas, it is safe to go 80 MPH when it is 1/2 mile to the next intersection!
So if the tire sidewalls say it is a 2012 tire, you should be good until 2019, then change them out again. Perhaps you can wear them out by 2018.
Have fun camping!
Fred.