There is a slight dent in the hood of my 2005 Honda Civic. If my life goes as planned, I will probably sell the car in less than a year. My question is simple, though maybe hard to answer: Does the cost of repairing a dent outweigh the difference in resale value? If it's cheaper to repair the dent, I'll want to get it fixed right away.
The resale value is mostly a matter of opinion and general impression. Some people want to buy a used car that is in pristine condition, others won't care about little dents. Some people care more about the age or mileage, others care more about the physical and mechanical condition.
Look at the dent. If it's down to bare metal, you need to do something about it before rust gets in there. If it isn't, do YOU mind driving the car with that dent?
Finally, don't base repair or maintenance decisions while looking at a hypothetical future resale value. This isn't an investment, it's a means of transportation. You might get T-boned tomorrow, maybe operating gasoline engines will become illegal or cost prohibitive 6 months from now, maybe insurance companies (in their infinite wisdom) will jointly and flat-out refuse to insure any vehicle more than 10 years old, or Honda's will be banned from the road (remember the VW emmisions scandal? They shoulda been kicked out of every single country where they cheated government emission certifications).