My 2010 4runner has original tires which is 11 years old. We are in Canada, so we swap to Winter tires for half the time. So, the original tire tread is not bad, still have a full 4/32 on all of them. But I heard tires should be replaced after 6-10 years as the rubber will rot and become unsafe. Should I replace them now? Looks like this is a $1k investment and no way to DIY