HI; I Am A 76 Yr Old Veteran Who Has

HI; I am a 76 yr old veteran who has been on pain meds for several years now, since my back surgery Jan/2009 on L3,L4,L5 for stenosis. My meds are Norco 5 times per day and Robaxin 4 times per day. Mt question is as follows; I have decided to refrain from those pain meds until completely out of my system. How long will it take for this to happen. I think I am not getting good results due to the length of time using these meds. So far for the past 12 hours I am tolerating what pain I experience. What do you think?
Gary Allen