Do old strings affect tuning and/or intonation?

[Schizoid75]

Do old strings have a negative affect on the tuning or intonation of a bass? I thought I remember reading something once that old strings can get bent where they contact the frets and start causing tuning issues. Anyone have any information on that? Obviously, I know that the sound will change as a string ages, especially round wounds, but are there other benefits to keeping newish strings on your bass?

Also, does it make a difference if we're talking round, flat, or tape? For example, do rounds develop kinks or dents, but flats or tapes don't?

I know there are people who have had flats or tapes on for years, so have you noticed any problems?

Thanks!

[Schizoid75]

Well, I did some searching and found a handful of posts where folks discussed leaving their strings on until the intonation starts to go. So I know that old strings can affect intonation, but what causes it? Is it simply dirt and oils? If so, then roundwounds would be susceptible to it while flats would be nearly immune. Or is it (as I suspect) kinks, dents, etc. to the string? If that's the case, I'm guessing that someone with high action who plays aggressively is going to notice their strings causing intonation problems before someone with low action and a light touch. True?