I think that's correct for 6061 depending upon which temper is desired. Normal precipitation age-hardening takes place over the course of several weeks and brings the material up to a T3/T4 temper. There are post-weld processes like quenching that generates this temper quickly. To get T6 temper, you need to do a solution heat-treatment at around 450C for a couple hours to dissolve some of the previous precipitation.