An elephant has a force of 50 to 100 pounds per square inch (psi) on a floor, while a 125-pound woman in high heels has the force of 2,000 psi.  That’s 20 times greater than the elephant.  Such force can damage any floor, not just hardwood.  Exposed nailheads are especially brutal to a floor their 8,000 psi is damaging enough to pulverize hardened concrete.

Knowing when your floor needs refinishing is more than just the look and feel, although it is usually the first indicator.  Below is test to see if the floor needs refinishing or not.  Pour a tablespoon or two of water onto the floor.
Does the water: Bead up so that you can wipe it up without a trace? Congratulations! Your floor's finish is doing its job!
Soak into the wood after a few minutes, darkening the floor only slightly? Don't panic, your floor's finish is only partially worn. Immediate refinishing probably isn't necessary, but keep a close eye on the floor.
Immediately disappear into the wood leaving a dark spot? If so your floor's finish is seriously worn and it's probably time to recoat or refinish.

Regular care is the best policy for maintaining wood.
Only use cleaning products deemed safe for wood.  Many cleaners have disinfecting and dirt removing agents that can damage and/or stain wood and wood finishes.  Most warranties from finish manufacturers are voided by use of oil soap cleaners.
Wipe up spills immediately with a lightly dampened cloth, then follow up with a recommended cleaning product.  For stubborn stains, lightly dampen a soft cloth with a manufacturer’s recommended cleaner or a generic hardwood floor cleaner.  Apply directly to the stain and repeat as necessary.
Never use a wax finish on top of a surface finish.
Care will depend on the type of finish used.  Always follow the manufacturer’s suggestions for care and maintenance of the finished product.
Keeping a clean surface prevents dust and dirt from scratching and grinding into the finish over time, thus reducing refinishing often in the future.
Keep all wood products away from heavy moisture.
Use felt protector pads on the feet of furniture legs to protect flooring from scratching and denting.  If furniture has casters, use non-marking rubber casters instead of metal or plastic casters, which can dent.
Caring for your water-based urethane floor is simple. Use a lightly dampened (not wet) mop or vacuum frequently as well as the finish manufacturers recommended urethane cleaner for regular cleaning (some urethane manufacturers recommend using a damp mop and some do not).
Never use a scrubbing or scouring pad that may damage or scratch any surface.  Use only those cleaning products and pads that are recommended by the product manufacturer or that are deemed wood safe.
For rustic faced antique wood such as unfinished beams, rustic cabinet lumber or dimensional lumber, dust and clean using a small hand broom or suction vacuum.  High pressure air such as a can of keyboard cleaner is also effective.  Do not wipe with a cloth, rustic wood grains snag the cloth and leave behind strands and fibers.
Throw rugs and dirt-trapping mats at exterior doors will greatly reduce long term wear on wood flooring, reducing refinishing/rebuffing and maintaining the beauty of your floor.  If using a throw rug or door mat with a rubber or vinyl backing, check to make sure that it does not dull or discolor your floor over time.  Some chemicals in rubber and vinyl can react with certain finishes.
Door Stops will protect siding and paneling (as well as any other wall covering) from door knob dents.

Ammonia-Based Cleaners
Dust Cleaners
Water & Vinegar Solutions
Never wax or use any wax-based cleaners or treatments on a urethane finish.