I personally will not submit if a person used in the past 12 months, and is still of the age where MJ use is considered almost a right of passage. For me as a security manager I see that as under age 24. I base this on my experience seeing packages rejected when HR had a bigger influence on who was submitted than I did as Security Manager. Once that situation rectified (intentional use of word) and I gained near final say (defer to the PM), and 7 years direct contact with clearance division. I have had them contact me on at least 3 occasions requesting I pull back a package and wait 6 months if the prescription use was less than 2 years. I expect a conduct letter for anyone admitting to non legal use and I process about 3 to 5 of those monthly. The person is not obligated to discuss the content of the letter but they often have questions and I am willing to assist.
Non legal drug use also seems to have age limitations. Use when younger than 24 appears (so far) to be treated as more benign than it is at age 45 plus. I base this on seeing denial of clearances and that being the only issue listed. Possibly they have other issues not disclosed. On occasion a person gets a SOR and asks assistance in appealing. I do so as it is a learning process for me. It helps me keep my fingers on the current pulse of denials, and appeals.
Equally, there appears to be a different standard if one sells drugs or the drug is in a higher category than MJ, or the use/sale occurred when cleared. Generally speaking if it is older than 10 years it is mitigated by time. Even more serious issues.
General rule of thumb I use is 12 months for random experimental, 24 months for regular but say weekend use, 36 months if they were a daily user and 72 months if they admit to moving bales of MJ. I have come across quite a few daily users, one who smoked before the interview. And smelled of it. Rejected. This resulted in a near perfect clearances granted record for me. I take the time to heavily screen. Prior to this HR was more about quantity not quality. My way reduces the amount of paperwork I push (electrons) and gives more return on investment of time.