Go ahead and call your heat-and-air guy now, and tell him you want your heating system cleaned and serviced. If we get a cold snap, hundreds of people will find out their heating systems died in their sleep over the summer. Then, every heat-and-air technician in town will be booked from dawn 'til bedtime, and you'll be shivering and thinking about buying one of those indoor-air-polluting, recliner-chair-igniting portable heaters.

I tell everybody who'll listen: Get your heat-and-air equipment serviced twice a year, once before the weather turns hot, and once before the weather turns cold. Service calls are surely cheaper than buying a new system years too early, which is what happens to people who don't want to pay for maintenance on their equipment.

Heat-and-air equipment usually lasts about as long as a dog, but mine is easing into its blind-cat-with-bald-spots years. Before your heat-and-air guy shows up, I suggest you do the following:

1. If your furnace-or heat pump-is outside, make sure there's enough room around it. In our part of the world, a lot of people are furnace-hiders. Either by bushes around the outside heat-and-air equipment, or by a little corral around it. Your service man needs at least two feet of walking, squatting, and working room. If you've got bushes, trim them back or dig them up. If you've got a corral, take it down.

2. If your furnace is inside, and you've got junk piled up around it, move the junk. Just about every day, I look in attics and basements, and find furnaces covered with junk. The same two feet of space is necessary for inside equipment.

3. Take a look inside the equipment. Gas furnaces have easily-removable panels. Take them off and look inside your furnace. Make a mental note-or even take pictures-of water stains, rust, and debris inside the furnace cabinet. When your service man is done, check again.

You're thinking, Why should I do that? Well, we find furnaces filled with rust, burnt matches, and cicada carcasses from 1998. Every now and then, we'll find the original owner's manual, singed, stuffed inside next to the burners. When pointed out, homeowners claim that they just had somebody clean the furnace. Sometimes, they even have receipts. One cure is to do your own before-and-after check. Another is to sneak up on the technician while he's working, and offer some refreshments. If he's doing his work, good. If he's sitting down smoking and talking on his cell phone, you might just need that before-and-after evidence. Just so you'll know: After a service call, the insides of a furnace should be good and clean. In the business, it's called "penny-bright."

Another thing you ought to check is if you have a mid-efficiency gas furnace: There should be at least an inch of open space between the metal furnace vent (the exhaust pipe) and anything that will burn. The specification for this one-inch clearance is written right on the vent pipe. Even so, a lot of heat-and-air installers and technicians ignore the specification.

It's easy to check for proper clearance. Just follow the vent pipe. Here are the usual offenders:

1. The vent is too close to insulation. Often, the vent is touching-or very close to-insulation on the ductwork. Insulation has a paper facing. Even foil-faced insulation has a paper backing. That paper will burn.

2. The vent is too close to a wall or ceiling. Wallboard (which is the same stuff used for ceilings) is covered with paper. It'll burn.

3. The vent is too close to wood. In basements, vents often are butted up to wood framing or subfloor. In attics, vents are often butted up to wood framing or roof decking.

Now, a recommendation for those of you who are about to find out your existing gas furnace is dead: Buy a high-efficiency furnace that can be vented through PVC pipe. That way, you get a unit that will be cheaper to run, and you won't have to deal with the costs, dangers, and installation headaches that come with metal vent pipe.

You heat pump owners should always buy the most efficient system you can afford. High-efficiency systems are generally better-built, last longer, and work better than the mid-efficiency systems.

If you buy the high-quality stuff, and treat it right, you just might get it to last as long as a good horse.