30 days use of pads

I am on my 3rd box of pads and intend to wait a week and start the maint. program.
How do you know if 30 days are enough? I received my test results and was positive for Benzene, Isopropyl alcohol, Copper, Mercury, Nickel, PCB's and was only negative for Arsenic. The pads tested were from my first box and I am on my 3rd box. There is no difference in the color of the pads though and only occasionally will there be any white on them.
Is it ever recommended to use them for more than 30 days or take a break and do another 30 days or just go on maintenance after the initial 30 days? How do you know without more testing if 30 days are enough?
Thanks Dr. V for all you do and all your help.