From what I have heard and researched, I thought it was 30 days for all. Not by weight. Someone correct me if I am wrong please.

I heard the same. That THC comes out of the system after a month, or so. Regardless of weight.

You guys are taking about stored in the urine/blood stream or whatever.

Drugs can store themselves in fat for a whole life time, or until the fat is lost Etc. There are many places that use techniques such as sweating the drugs out to loose the drug-containing fat cells. Search it up online.

If your worried about fat, which you shouldnt be cause alot of places dont take the time to test fat cells for drugs. I'd be more worried about your hair, the hair can store all residue from a drug until that hair is cut off and new hair grows in.

THC stays in your system for 3 weeks, a little less sometimes if you only had a toke or two, but even then it will be at least two weeks. Id say 3 just to be safe. Dylan is right however about your hair, it will stay there until you cut it.

Yes, steroids are one of the drugs that can stay in the systom for 18 months. Weed is not one of them. And yes, there are certain drugs that can now be checked through the hair foclicle. But they are limited.
Search it up on online.