One failed within a couple of months.
One failed after a year and a half.
One failed after about 3 years.
Two still work after 2 and a half years.
One still works after 4 or so years.
Another still works after 4 or so years, but has only been used for a handful of hours (it's in a cupboard).
So that's a failure rate of 43%. These things are supposed to last longer than the bulbs, which have a rated lifetime of 5 or so years. I'd have expected them to outlast several bulbs, otherwise what's the point of separating the electronics and the fluorescent tube?
I think I'll see if I can get the landlady to replace the latest dead fitting with a classic non-CFL-only one.