They can last a very long time however they do start to sound different so I change mine every 4-6 months or if one breaks I change all of them right away
Standard response to the question
ought to be 'How long is a piece of...'!
As everyone will tell you,when they no
longer sound the same,ie not so bright,
not so loud,whatever it is that you like
about the strings you use:when it is no
longer there,time for a change!
They last forever. I hear a lot of companies are going to start building their products from ukulele strings so everything last forever. Wouldn't be very good for business, but it's a step in the right direction for the population.
I hate paying for shipping so I usually buy strings to get above the $50 mark at Elderly, so I have lots of strings on hand. I like experimenting with different strings to see what sound I get so probably change them more often than needed