Do you refer to an existing study here? Maybe you can share the source with us.
For an investigated period of this length, classic interferometry (InSAR) is hardly applicable because of temporal decorrelation (except for urban areas).
It is true that the detection of displacement is limited by the size of the wavelength. If you are working on an urban area, I would at least consider using several image pairs to reduce the temporal baseline and the effect of atmospheric effects in single pairs).
In fact, PS InSAR is more reliable, but requires a lot more images (e.g. a monthly base for the entire period), and time to get into. The preprocessing is currently not implemented in free software with a simple user interface. We collected instructions in this here: StaMPS - Detailed instructions - #2 by ABraun
It took me half a year to get to my first result, to be honest, because I was not used to using Linux and Matlab (required for the processing) using the required scripts. Even after that, I am quite insecure about the many different parameters ad outcomes.