I take sub to keep out of withdrawl. If I use, I'll have about the same tolerance as I had last time I used. Even after sub. So for example:
Day 1, I have been bingeing for a week on heroin (or more likely fent) iv'ing 2 to 3 stamp bags per dose, 10 bags a day or more. Then I run out of dope or money to buy more dope with. I wait until I can feel withdrawls starting e.g. elevated heart rate, uneasiness, anxiety, cant hold still or sleep, so on. I take the first dose, 4 to 8 mg sub. The first dose of sub I make sure is high so I won't have any precipitated withdrawl. That lasts 24 hours. Then second dose is half the first dose. That lasts 24 hours. Then the third dose is half the last dose. So at this point I'm at my maintenance dose whish is 1/8th of an 8mg/2mg sub strip. I take 1/8th every 24 hours and I never end up in withrawl. And that also makes your sub last a long time so you can horde it (which every opioid addict should imo). If and when I decide to use again, my tolerance is about the same as it was in the middle or end of the last binge. Never assume that you tolerance is high though. Always assume you have little to no tolerance and go slow in the beginning. Better slow and titrate up than overdosing. I never have any problems with the sub "blocking" opioid effects. It might be because I'm using very potent opioids and my maintenance dose is so low, but that's my experience. Imho, you shouldn't ever have a maintenance dose so high as to take 12mg a day. Always reduce your dose as fast as is comfortable. You'll be surprised at how fast your body will addapt and be comfortable with much lower doses of bupe.