The Mayall 4-meter telescope on Kitt Peak is a successful and productive telescope now approaching its thirtieth anniversary. Originally designed at 150 inches, built at 158 inches, and with an effective aperture or 3.81m, it is from the generation of thick mirror, equatorially mounted telescopes. At a moderate altitude site, the Mayall had in the past upheld the prejudice that ground-based observing delivers about 1" seeing at best, and that it is no surprise to be considerably fuzzier. Changes in engineering, computer control, and our understanding of telescope seeing, have led to the new generation of lightweight mirrors with complex active support and advanced thermal control, running on altitude-azimuth mounts inside compact, low-volume enclosures. Such telescopes routinely deliver sub-arcsecond seeing, often down below 0.5" even from 'traditional' sites, and even sharper from higher and more remote sites to which access has been developed over recent decades. Nevertheless, what we have learned can be successfully applied to older telescopes: the Mayall telescope is a case in point, since it now regularly provides sub-arcsecond image quality. We discuss the significant improvements in thermal management and active control of the Mayall system over the last several years, as well as the difficulty of evaluating such changes, especially separating different effects. We also discuss future adjustments to and tuning of existing sub-systems, possible changes to the telescope environment, and planned new features. It takes effort and continual attention to detail, but older facilities can still be world class.