I own both the original QUAD Electrostatic loudspeaker (3 pairs), & its immediate replacement, the ESL-63 (2 pairs). I have left the originals on for over 2 DECADES now, not a problem! But the ESL-63, & various other electrostatic loudspeakers I either have owned, still own, or at least have some acquaintance with, are a different story. But for different reasons, too. Other Electrostatic loudspeakers, with the exception of Acoustat, do degrade over time. My original Martin-Logan CLS's had a silly "standby" circuit that was also in the signal path, degrading their performance in more ways than one! So screw the warranty, out it went. From 800VDC in "standby" to 3200VDC full time. I still found it a bit dull & lifeless, the speaker rolls off noticeably (-3db @ 10kc/s), so I added an extra diode leg to the voltage multiplier: 4000VDC even. Better, so I left it at that. All was well for many years, somewhere between 5 & 10 anyways. THEN minor trouble started: increasing leakage during high humidity conditions (hissing, popping, farty background noises). Near as I could tell, the open panel design picks up airborne contaminants. I don't smoke or burn incense, but that only slows the process down, not eliminates it. Attempts at cleaning the diaphragm (very carefully!) showed substantial improvement. But really, bad designs like these have a finite lifespan. Ditto later-model Audiostatic speakers. Left in bright, direct sunlight through patio doors 2 hours a day for about a year resulted in a 10db loss of measured efficiency & as Audiostatic went tits up in the interim; a total loss accompanied by some wailing & gnashing of teeth. Not me, a friend. I warned him! Didn't know for sure, but had a BAD feeling about that speaker placement. Post Mortem suggests that ultra-thin conductive diaphragm coating has some photosensitivity. Don't leave electrostatics baking in the sun! Plugged in constantly. Or, NOT! Then there is the QUAD 63 "family". Including the 980, 2800, & 2900 series. They all use the exact same elements, btw. They are time bombs! You get 10, max 15 years & then the plastic starts to bio-degrade. Plugged in, or NOT! The plastic gets brittle, like those new shopping bags. The diaphragm splits, peels, flakes apart! QUAD is mum, serious denial last I inquired 5 yrs. ago. LOTS & LOTS of used QUAD's for sale, ALL "just need minor TLC". TLC my ass, they need a $4000+ replacement of the 8 panels, or $6000 for 12 panels if you have a "larger" model (989, 2900 series). It's not charging that kills electrostatics. In order, it's physical abuse (bending, twisting, falling over), electrical abuse (old QUAD's can be arced by excess volume), ingress of conductive contaminants (dirt, okay? Just...various kinds of DIRT!), but mostly, DUMBHEADS using the WRONG GRADE OF PLASTIC! (Hey Boss! I got us a deal on that big roll we need for our next run! DUHHHH!).