Walk the property once with a phone camera and photograph the serial plate on every major system. The manufacturer date code is stamped on nearly everything mechanical, and it’s more reliable than a listing sheet.
A single aging system is a scheduling problem. Three of them arriving in the same eighteen months is a budget problem, and the difference is only visible once the dates sit next to each other.
Anything sitting above or beside finished space carries a higher cost of failure than its age suggests. That’s the judgment a lifespan table can’t make for you, because the table doesn’t know where your equipment sits.
You give up a little remaining service life and you buy back the ability to absorb the next failure on your own schedule. That trade is nearly always worth making.
None of this requires software. It requires the dates in one document, reviewed annually, with the next two decisions written at the top.