Dear @ABraun. I have used 27 Pairs with 12 days Temporal Baseline except 2 pairs of 24 days Temporal Baseline. in a nutshell this was one year data processed. The man and max are 10.4cm and 16.3cm per year respectively. where Red shows minimum, yellow Zero and Blue Maximum. Kindly look at the picture is that okay?
using 27 pairs will at least reduce atmospheric effects of single pairs to a very small degree.
I cannot tell you if the results makes sense in your area, I have never been there 
Maye you should compare it to other studies and see if the patterns you observe in your data match with their findings.