Vintage 1601 service

I just received back my grandfathers 1973 1601 DJ for service. The AD told me the warranty does not include timekeeping due to its age.

I noticed the power reserve lasts about 24hrs while most report 40-ish.

Shouldnt they have at least checked/replaced the main spring? From what I was told, this watch was sent to the Dallas facility for "vintage service".