When it fails (?).
As per I read, there some cases of failures and it leaves you in the field, giving no usable warning. At some point it may make sense to change in prevention, but it is electrical and much more expensive (6-800$) to change than a regular one.
It would be interesting to determine a point in mileage where at least 10% failed. Then I would be tempted to do it.
My guess so far; not enough info.
2007 E90 AW 323i Step | Lowered 1.25"/1" | BMW Performance Exhaust | Debadged | Scangauge II | Style 162 18" & 161 17" wheels & rear 15mm spacers