Surely this is a "Ship of Theseus" type of problem i.e. to achieve this longevity you have to continue maintaining it until it is no longer (philosophically) th

Surely this is a "Ship of Theseus" type of problem i.e. to achieve this longevity you have to continue maintaining it until it is no longer (philosophically) the server you began with. Keep its software and configuration practices up to date, upgrade and replace components. Servers that have lasted 10-15 years have rarely done so with at least some maintenance, and the less performed, the accumulated legacy of being out of date is more likely to sink it completely.