One of the - err - beauties of this question is that it means such different things to different people. Perhaps smaller stations will be changed less because there's less to be changed. I looked at some of the smaller stations on the Looe branch / never had any goods sidings so nothing too change.
Funnily enough, all the small stations on the Looe line have changed in the last forty years - Coombe Jn lost the second line/loop in the early 80s, St Keyne and Sandplace had new brick shelters with canopies erected in 97/98, Causeland had its shelter pebbledashed around the same sort of time (I think) and all bar Coombe Jn got permanent lighting for the first time around 2003.