I have changed titles a lot in my experimentations. Here is what I found works:
1- If the title change creates a more 'natural' reading experience (so change from Blue Widget to "Buy Blue Widget on Sale at Discount Prices")
2- If the title change increases CTR
So far, title changes which fit into 1 AND 2, were overall positive within the first few weeks.
I would say that niche granularity is on the increase. So it wouldn't surprise me at all if changes on topics deemed to be 'static' were seen as highly suspect, while topics deemed as 'dynamic' got more leniency.