You already know the roof will need replacing. What you probably don’t know is that your water heater, your furnace, and your roof were all installed within four years of each other, which means they will reach the end of their service lives within four years of each other too.
That clustering is the single most common reason a maintenance budget that looked comfortable for a decade stops working in one season. It’s also the most predictable, because the install dates are usually recoverable from the equipment itself.
Before you estimate anything, walk the property once with a phone camera and photograph the label on every major system. Manufacturer date codes are stamped on the serial plate of nearly everything mechanical, and they’re more reliable than a previous owner's memory or a listing sheet.
A water heater at year eleven is a scheduling problem. A water heater at year eleven in a finished basement with no floor drain is a different problem, and the cost of getting it wrong is not the heater. This is the judgment that a component lifespan table can’t make for you, because the table doesn’t know where your equipment sits.
Take the two systems closest to the end of their range and move one of them forward by a year. You lose a small amount of remaining service life and you buy back the ability to absorb the other one on your own schedule. That trade is almost always worth making, and it’s invisible unless you have written the dates down in one place.
The goal is not to predict the failure. It’s to make sure two of them never land in the same quarter.
None of this requires software. It requires the dates in one document, reviewed once a year, with the next two decisions written at the top.