NHK295M - I ave a Lelit Elizabeth. It had a Cafelat silicone gasket for the past 4 years. Still there, and going strong.
There’s no point changing the gasket UNLESS you damage when removing the shower screen - something I managed to do a couple of times back in the day when I had a Profitec 700.
Just make sure you keep that gasket and shower screen clean by removing it twice a week or so.
edit: Different story for the rubber ones. They will usually go hard after a year, and you’ll notice. As HarveyMushman said, replace those every year or so in a home setting.
Although I think @Doram has managed to get 2 or 3 years out of a rubber gasket on his MaraX, and that’s still going strong!