I haven't needed to set the Purifier on full blast for more than 30 minutes, but if I do I'll keep an eye out for it.
Yeah, upgraded from the stock infrared sensor to a laser one. Found it on Taobao so you might need someone who knows how to read Chinese to order it for you.
If your current sensor is working properly then there's no need to upgrade, I think mine was broken so it made sense for me. The stock one was gonna cost me 120 RMB and this one cost me 165 RMB so I thought I'll have a bit of fun for an extra 45 RMB.
If you still want to get one, go on Taobao and search for one that has a PBC pre-soldered on made for the Xiaomi air purifier 2. This is the guy I bought it from: http://m.tb.cn/h.Wu9meOA
Edit: I used one of the official Taobao ship forwarder, and it cost me like 11 RMB and picked it up from a nearby pickup point. 4PX was the ship forwarder, I think.
Xiaomi recently upgraded their Mi Home app to require permissions to access the calendar- can anyone who has installed the upgrade comment on whether there's additional functionality that really makes use of calendar access?
I think you can just deny them. Those might be needed for other smart devices, but I see no purpose on the purifier.