A long term review would be interesting.
I've tried 2 xiaomi devices and since the new app they regularly fail to sync and discard all data even when failing which means to big gaps.
Sometimes only a factory reset of the band and a repair helps.

I steer clear of xiaomi devices for this reason now which is sad cause I actually like most of their hardware.

Latest band tested was the mi band 8, it has one of these drop outs almost every week, destroying sometimes 2 - 3 days of data.

No comment on the accuracy of sleep tracking? 😒 Accuracy of sleep tracking from Smart band 8 onwards has been poor.

As adults it is very difficult to get 2.5 hours of deep sleep though the Smart Band 9 reports such high values.