I'm sure you'll get as many suggestions as reply's on this subject.
My two cents worth is that it really depends on the make and models involved as to lifetime. Though manufacturing technology has improved when I was supporting West End productions in the early 00s we had a mix of Sony,
Sennheiser and Samson products. I had a regular task of replacing body shells of the Samson systems and never had to the same on either of the other brands. Sweat was the real killer for all models and all levels of product. I now support a high school
theatre in NYC and we have
Shure everywhere, ranging from ULX to UR beltpacks. Prior to that I had all
Sennheiser G3s at another school. My most recent acquisition was a QLX-D
system which features metal body
build that rivals the UR product in my opinion (I dream of the Axient
system for my main
theatre).
While you don't specify the
Shure range you have I suspect the systems you have now are probably plastic bodies. I can't say I'm surprised they are failing at 4ish years given the work load. Our plastic body
Shure TXs look ugly after about the same age. I feel that
Shure are targeting the MI environment with their lower end products and expecting usage of a show or two a week. My recommendation is to avoid plastic bodied transmitters and
switch to something that has metal cases regardless of brand. When I was specing the
system that we ultimately purchased the QLX-D for it was between the SLX and QLX-D ranges and I'm glad I able to get a budget increase when comparing the
system costs for 10 channels.
Dan