A long time. I have had the same set on my acoustic for three or four years. I do not play the bass every week but it has had its share of play time.
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I ran a set for almost 10 years on my fretless, which was a bit too long. They actually developed flat spots in the tape covering from overuse. Heck at $20-ish per set it may be good idea to swap 'em out every year or two just to be on the safe side.
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No Ma'am, I'm not as talented as the other guitarist in the band. That's why he gets six strings and I only get four.
I'm at 8 years right now with my La Bella tapes on a Fender Jazz 5 and they still sound, look and feel new. The only watch out is that you might have to have the nut filed a bit to compensate for the thicker strings and they may not fit thru a string thru body (mine barely did). But they sound great and are worth the investment.