here is my personal experience with tolerance. Now, this strictly speaking for heroin. If you wait 3-5 days without use your tolerance will go down maybe a bag less: you will catch the same high minus a bag. So, for me that would be 5-6 bag normally and after that 3-5 day clean period 4-5 bag would give me the same high . After maybe 2 weeks you could probably do half so the 5-6 bag shot would be 2-3 bags. From then on it kinda decreases really slow. Maybe a 2-3 month and you would be at the 1 bag level. To get to pre-opiate level I am not sure because I never got there or been clean long enough to find out. However, the longer you have been on dope and more dope you use the longer it takes to lower your tolerance. I remember when i first start shooting/ I would do a 3 bag shot that would get me in such a serious nod that it was close to od'ing; thus, I stuck to 1-2 bags shot exclusively . Fast forward a about a 1 & 1/2 years during my peak here a minimal shot is 4 bags and really good shot is 7-8 bags. So, in that time of 1 & 1/2 years my tolerance tripled . But there are other aspects: the high I would catch in the begging would last for like 8+ hours, Now that the 7-8 bags shot might only be for 5 hours, at most. Plus, the rush isn't as good. So, if your just trying to get your tolerance to a reasonable and affordable level stop for 2-4 weeks and it should be cut in about 1/2. But after that 2-4 weeks period the decline seems to be exponential and not linear. At least, that is how it works for me.
Ohh and you can't forget about craving during my peak I was using 25-50 bags a day, but during the beginingg I was using half a bun. The more you do the more you crave(^cubed).
Anyways this is my personal and subjective experience "so, don't quote me, boy!" j/k