From what I read of your original post you are already destined to become a fellow junky. Welcome to the club. I'm not sure which opiate you're using, but don't trick yourself into believing you're any better off than a heroin user. Vicodin, Percocet, Morphine, Heroin, Fentanyl, Hydromorphone..... it's all the same addiction at the end of the day. No matter what route of administration you use.
Keeping your tolerance down? If you keep using, even only on weekends, that will still be impossible. It may be possible to keep your tolerance down using once a month, but good luck sticking to that. Your best bet is to avoid the temptation of higher doses. Also, use potentiates rather than higher opiate doses. Eat half a valium with your opiate. Drink some white grapefruit juice with it. Fuck, even an anti-histamine like diphenhydramine (primary ingredient in most OTC sleeping pills) will do to increase your opiate buzz nicely. It may not be quite as clean, but the honeymoon phase is called a phase for a reason.
No ill will intended. Best of luck. I hope you can do what I couldn't. At least you have the luxury of knowing what you're flirting with.