As the decline in performance is gradual you will seem to think it is working fine, when actually it is not. A lot of owners also do not use the system frequently, when they should do, as the gas has lubricants added that keep the seals in order. If you do not use it the seals dry out and you loose the gas. The compressors draw on the engine is also minimal and will effect mpg no more than driving with the window open, probably less, so a false economy not to use it. I always run the car with mine on and stick to a 3 year re-gas. I did this with cars prior to the Yeti and now with my Audi A3. When I'm in France in the summer and it hits high 30's, even low 40's c the car is nice and cold. The cost advantage lies with the Yeti owner over more modern cars when it comes to a re-gas as you are faced with a £60/70 bill as opposed to a £120/140 bill due to the different gas used in post 2019 ? cars. Do yourselves a favour, use it, re-gas every 3 years and make the most of what you have in a great car. Colin