Until they no longer sound good to you, or you notice that "something's wrong". I had to replace a tweeter on one of my speakers a few years ago; both recognizing the problem and accomplishing the replacement were "no-brainers".
How long should high quality speakers last?
My Zu Omen Def MKii (rev B) are going on 13-14 years old. The speakers sound wonderful. I have no intention of parting with them. The speakers came with the latest ZU tweeter design. How long should I expect the speakers to last without any issues? I do not abuse the speakers and run them with my Luxman 595ase amp.