How long do IPL devices themselves last? And how often & long do they need to be used? Do you ever stop using them (because you no longer have to) or is it just an alternative to shaving?

I was just looking at an ad for a Braun Silk Export Pro 5 IPL device. The box says "5 year warranty" but also says "good for 1.5 years of smooth skin". I'm not sure how to decipher that. (The description only says 1 year.) What am I missing? Does the treatment last 1.5 years, or the device?

I know it requires repetition, but when can you expect to stop? (I'm sure it varies by machine and person and hair color, etc, but there must be some boundaries.)