HOWEVER: law enforcement agencies are quite a different story and tend to be much stricter in their requirements. Some, like the FBI, have public drug qualifier policies you will need to meet  and there is no wiggle room (1 day short of 10 years and you're 100% ineligible). Some agencies do not publish this policy (i.e. Secret Service) and you have to guess whether you're eligible.
The most important thing to remember is that whatever you admit on these forms will be on record for review by any agency for the rest of your life. DO NOT try to give extract or estimated numbers of usage on your SF-86 unless they are exceedingly low numbers. You can be honest with your background investigator during the followup but there's no reason to commit those things to writing on a form that's likely to be easily accessible later on.