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It's been around for a while, but it's trickled down to more boots and more shops are willing / able to do it.
When I was working in a shop it wasn't common that customers came with their own boots to rent just just skis, but whenever they did it was a fun lottery of what condition they'd be in. I had to reject a few customers because their boots were so worn or old we couldn't safely fit them to a binding.
Though heat tech has been around for decades. Comfy liner really works as you can get different size inner so perfect fit.