Lansche plasma tweeter replacement every 5000 hours.

It does seem to be the problem with this type of device - there's been a number of different ones made over the years but only a couple of manufacturers survive - useful background here

The ozone issue often gets brought up.  Although these types of speakers produce ozone it can be readily catalysed back to O2 using several methods and/or adsorbed by activated carbon.  Ozone is very unstable and typically only lasts around 20 minutes - it is easy to smell and avoid.  There's more than ozone to worry about (NOx for example) and many other things that makes these devices challenging to design (see

for more detail). But these issues are what makes designing them interesting and the problems can be overcome.