"hey would understand that over "time" things change and would maybe like to "mark" these changes in some way, therefore creating a panel that also was built up and changed over time."

Yes indeed, I can accept that, but it does rule out a lot of things that dont change much - stars and springs for instance.

But there's a fifth dimension on many panels too. It can be seen in the fact that some older motifs appear to be vandalistically overwritten by newer ones. In other words, there's a "respect" dimension - the meaning and importance of the marks appears to change over time, i.e. half the marks we see cant possibly be connected in time or intention to the other half.