According to a note jotted on a slip of paper in my violin case, the last time I replaced all four strings was one year ago. Since that time I have swapped out an unwinding A string for a new one, but the other three are past their prime, to say the least. It's just that with strings being so expensive, and the fact that I don't do much solo playing these days, I kept putting off the inevitable.
Unfortunately, in the past year the prices have gone up. The four strings that used to cost me $60.00 are now going to cost me $82.36! Sigh.
Frugality just doesn't seem to go hand in hand with owning and maintaining a reasonably nice violin. (My former teacher used to urge me to upgrade to a nicer violin that would "only" cost me about $40,000 or $50,000.)