different people have a different amount of acidity they produce in perspiration. some can ruin a set of strings in a day and others can play them a long time.
I suggest wiping the strings down with a clean absorbent cloth after you finish playing each time to help them last longer.
There are many variations to “good sound”. Be your own judge and learn to listen to your own instrument. Some people can’t stand the ring and sustain of a new set of strings and don’t change them until one breaks and some play with new strings every day or two.
Each instrument can treat strings differently also. I had one banjo that was too bright until the strings had been “played in” a bit, and another that needs new strings quite often to keep having a good ring to it.
older strings can tend to be hard to keep in tune and make note correctly. They also lack sustain.
Experiment with different amounts of time between string changes and find out what suits you, your ear, and your instrument the best.