Service agreements lack sex appeal, but they provide warm companionship in a cold economy.

The night before writing this, I watched a big chunk of “Life After People,” a quirky production on the History Channel detailing what would happen to man-made structures and the surrounding environment were people suddenly to vanish into thin air.

The future in this fanciful scenario belongs to roaches, rats, cats and bigger wildlife. As for all those skyscrapers, bridges, tunnels and other miracles of modern engineering, the program suggests they would deteriorate faster than I would expect.

Experts narrating the downfall pointed to some things most of us never would have considered. For example, without building temperature regulation and the absence of routine maintenance, sealant that holds windows in place would go through expansion cycles that put lots of stress on glass panes. Even without high winds and fierce storms, after a few unattended decades, most windows in modern high-rises would be exploding of their own volition. The rest of the building shells would last a century or two but then start collapsing one after another due to the effects of weathering.

The message here is that without human intervention, things fall apart quickly. You don’t need to watch that TV show to realize this. Much of the science behind “Life After People” is based on experience in the real world with edifices that have been neglected for a long time.

Quaint colonial attractions like Williamsburg would be unrecognizable ruins without restoration efforts.

The famed Coliseum has stood for a couple of millennia as a tribute to Roman building skills, but tourists have to be content viewing it from the outside at a distance because the facility is on the verge of collapse.

The Egyptian pyramids have managed to last thousands of years longer only because they are situated in one of the planet’s most arid climates.

Mayan ruins in humid Central America have been abandoned for only about half a millennium but already are overtaken by jungle and rot.

All this got me thinking that everyone who works in building maintenance deserves a raise!

It also got me thinking about all that stuff I’ve been reading for years about our nation’s water and wastewater infrastructure falling apart. Authorities estimate that about 20 percent of our drinking water gets wasted due to leakage - this at a time when water is on the verge of rivaling oil as the world’s most contentious resource.

The Congressional Budget Office has estimated it would cost between $20-40 billion a year to bring our drinking water and wastewater systems up to snuff. Estimates by the Associated General Contractors of America range even higher.

That’s a lot less money than it would take to conquer France, and the urgency to spend it begins to resonate whenever you hear about water main breaks that tie up city traffic for days, which is happening with increasing frequency.

No matter. Satan will be throwing snowballs before that much money gets appropriated for this purpose. For one simple reason: infrastructure has as much sex appeal as the Wicked Witch of the West.

Nobody can accuse our legislators of being stingy with our tax dollars. It’s just that they like to spend it on sexy stuff like new buildings and roads that voters can see. Sewer systems don’t get named after politicians, and I suspect most would decline the honor no matter how apropos.

Routine maintenance is a tough sell to politicians. They’re like the rest of us kids in preferring to play with new toys rather than clean their rooms.

All of which brings this message to its ultimate point - it’s a good time to start selling the importance of regular maintenance to home and building owners. Business for most of you has taken a large tumble or soon will. Residential construction work is a dim memory in many markets, and with the economy headed as sharply downward as it looks at this writing, home and building owners will be deferring repairs and renovations until they see light at the end of the tunnel.

But just as health club dues can stave off major medical bills, service agreements can prevent budget-busting disasters down the road.

Contractors who have sold a lot of service agreements appreciate the warmth they bring in a cold economy. Their customers ought to be thanking their lucky stars as well.