Agree with this, exterminator took care of some I had many years ago. He came once a month and it took several months to get them all killed off. When he thought they were irradicated 100% he gave me his cell and said "If you see ONE roach, call me, and I will come back that day and you won't be charged". This happened a couple times and he kept his word, came back because I saw ONE roach and didn't bill me. The single ones I saw at the end were dieing, you could tell. They looked like they had been married to a crazy wife for 40 years and were ready to die. After a couple times of coming back for one dieing roach, I never saw another one again.