Having only owned the smaller 2 to 4 kw units..., JRC, Furuno, Ray
The electronics in the displays/processors do not seem to last as long as the antenna arrays.
that being said, frequent use helps prolong the life of most electro mechanical devices. A radar powered off for 8 months is a long time. Warming it up and operatiing once a month is far better for the devices. Power cycling 12 times a year extra is not a significant shortening of component life, and the benefits are great.