When you first get methadone they always start you off low...like 30mgs which is never enough...then you have to start asking for dose increases. And once you reach 50mgs the clinic us legally obligated to hold you at 50mgs for 7 days before the next increase. Once youre past that...the idea is to get you to a high enough dose where you feel comfortable and don't feel like using.
During the initial phase (30mgs-50mg) I continued to "top'-off" with dope bc the dose wasn't working. Once you finally get leveled off you feel alot better with less ups and downs.

Using dope on top of your dose will increase your tolerance for sure. Making it a bit unpleasant when you stop using and rely only on the methadone. But its usually pretty easy to get your dose bumped up 5mgs...its a slippery slope though.