iPhone ringtones can't last longer than 40 seconds. Yes, you can extend the duration of your personalized ringtone on any iPhone with any version of iTunes. From what I've read and from personal experience, an iPhone ringtone can't last longer than 30 seconds. I usually do mine for 29 seconds. I never tried 29.99, but I guess it would work.
As I said before, when I made a tone that was 31 seconds long, iTunes prevented me from uploading it, saying it was too long. I'm not sure how people have a 40-second one. Perhaps Apple's built-in tones are different.
