Five years ago, we went looking for a 727 PIC, all the resumes came from guys 65+ years old... almost all were not current.
I think that as new aircraft arrive on the ramp, the better flight departments and pilots will migrate towards them. For a while, pilots may stick with the older iron, but as a general rule, after 10 years, the good jobs will be with new equipment and after 30 years, the only place to find these antiques will be the eccentric departments staffed by people who can't get a job anywhere.
With an airframe age of 30-40-50 years, I can't think of a single 727 or GII job I know of where the aircraft are well maintained and the crew is paid well ( or paid on time). Why would anyone want this unless he was unemployed or starting out?