They can last a lifetime, but you may need to replace a driver or components over the years. Some plastics, foams, glues, etc degrade over time regardless of the conditions they are kept in, so not uncommon for things to fail over decades. I still have my Polk SDAs bought new in 1987 and have only had to replace a few drivers. I've gone through a number of other speakers over the decades as well and rarely any issues, and they have always been kept in an air conditioned house as well. As long as you are not obsessed with getting a perfect OEM original replacement part when needed, you'll be happy. That said, replacing components sometimes provides an even better performing component compared to the OEM part from decades ago.
How long do speakers last?
I ask because I have an opportunity to buy a pair of Von Schweikert VR-33's for an insanely good price. I get it: "it depends how hard they have been driven", but judging by the condition they were very nicely taken care of. My only concern is that will need repairs in the future whereas I could just spend that money on new speakers. On the other hand they sound fantastic. Just curious about the lifespan. They'd be a nice upgrade from my Klipsch bookshelves / sub combo.