Relation between time period of images and results of deformation


I have been processing Sentinel data in order to get deformation (‘v-do’), for three periods of time, each one includes the others.
The process used snap2stamps and StaMPS in Matlab.
The area in concern is a city next to the sea.
The first period include 7 months, the second perios 13 months and the third period - 36 months.
I wonder about the deformation scale - why does it change so much?
And why does it has invert-proportional relationship between time period and deformation limits? If I take a longer period - would the scale decrease more?

7 months:

13 months:

36 months: