You may need to have your hardwood refinished if:
There are deep scratches, pockmarks, or dull spots. These marks are more likely to show up in high traffic areas like entrances, hallways, and family rooms. They can be caused by high heels, moving furniture, or simply walking over an area too many times. Over time, holes and scratches can become worse.
Your floor is getting harder to clean and shine. The problem with holes and scratches is that they can collect dirt, dust, and grit. Not only will these particles wear your floors down faster, but they are also harder to clean up as they get caught in your flooring. Even polishing your floors won’t do much if you need refinishing. If you notice duller, dirtier flooring, you may want to have your hardwood looked at.
Your finish doesn’t pass "the water test." An easy way to test your finish is to take a small cup of water and drop a few droplets onto your hardwood’s surface. Wait several seconds and take a look at the water. If the droplets soak in quickly, the finish should be replaced. If the water sits on the surface, your finish will probably be fine for a bit longer. You can repeat this test in various parts of the home.