How to tell when your strings need to be changed!

[Quickstep192]

I’d picked up my nylon crossover today and to my great surprise, it was in tune!

At the same time I noticed the bass strings are showing signs of corrosion and the trebles are sounding kind of dead. When I change strings, I leave the package in the case so I know what’s on there. When I checked, I noticed that the strings are coming up on a year old!

So, when the strings stay in tune, it may be time to change them

[mtdmind]

I usually change them when the color of the strings don't match the color near the headstock

[Carey]

Except for the low E, I leave strings on until they either won't play in tune, get scratchy (high e), or break. I like the sound from broken-in strings better, IOW.
YMMV.

[Dogsnax]

I don't have very long nails and I've learned that my basses wear out about twice as fast as my trebles. Therefore, I change basses when they the intonation gets really bad (corroded, etc) - trebles get changed every other set of basses.

[Neal Pert]

I tend to like the sound of strings toward the end of their natural life. I like the tone to be less brilliant and more dead and woody sounding because it matches my dead, woody voice better. I usually change when I start having intonation problems.