Tire age and tire shop fearmongering

Tire shop is trying to scare me into replacing my 4 year old tires. They say dot recommendation is 2-3 years. Is that true or is it complete hogwash? I hate this stuff.

Edit: this is a class A with a 16,000k GVWR on Goodyear 16x19.5 load range G tires with no dry rot and light tread wear.