Nice nickname ! How do you recognize a good GSM radio engineer ?
Headaches, Hair loss and Sterile :))
More seriously, the answer is in 3GPP 45.008
Chapter 6.6.2 Path loss criteria and timings for cell re selection
ii) b. in case of a cell reselection occurring within the previous 15 seconds in which case the C2 value for the new cell shall exceed the C2 value of the serving cell by at least 5 dB for a period of 5 seconds.
Basically, it means that there is an anti ping-pong mechanism during reselection, which lasts 15s, and applies a 5dB margin to all neighbour cells.
Do you agree ?