Hi Tanyar,
I have a very similar situation to you. Double mastectomy in March 2013 and seromas on both sides just below the scar lines that needed draining regularly for 5 months. Initially I was drained about every 5 days but eventually the amount drained became less and I could go 2 weeks between treatments, and then they stopped producing fluid, and are now just hardish tissue. I don't know if these slightly swellings will ever diminish, but I am hoping so. Good luck!