I can believe 16 months from a set of nylon strings. I have some that went far longer than that. I have an ukulele from late 2008 / early 2009 that still has the factory set of strings on it, and it has seen a fair amount of play time. It is not my primary ukulele, which sees about 4-6 hours per week on average - still has the factory strings from last December. The low G string gets changed about 3x as often as the pure nylon ones, mostly because the windings wear.
I kinda hate changing nylon strings, since they take so long to settle and hold pitch. In fact, I have a classical guitar (gifted to me last winter) currently awaiting new strings, but it takes me a while to work up to it.
