There are definitely tolerance levels that are permanant and you don't need to take stronger meds for it to happen. When I first started having back problems in 1991 1 5mg vicodin would make me blissfully pain free for hours. I took the regular strength hydro for aboy 9 months and was up to about 2 to 3 5mgs every 4 hours. Stopped taking them for about 2 years then my back started to act up again. At this stage 1 5mg did nothing for me and had to take at least 2 for any effect. Now after being back on opiates due to constant cronic pain for the last 4 years I need at least 2 to 3 10mgs every 4 hours to find pain relief. I just started on MS-Contin this week a fortunately have found that 1 30mg tab does quite well for me every 12 hours.