This Swiss data is the best currently available about maximum daily heroin dosages when humans are given nearly unlimited access to the chemical. Using their data, it appears the actual ratio between initial doses of heroin, a low of 5 mg per dose, and highly-tolerant maximum daily doses of heroin of about 500 mg, this is a 1 to 100 ratio. But it also ignores the difference between single-dose use and repeated dose use. In the same way that its easy to finish off several bottles of wine over the course of several hours, while few ever drink several bottles of wine in just a few minutes, heroin users who are using throughout the day will go through a lot more heroin. So its inappropriate to compare single-dose initial values to daily-ingestion amounts. The increase between no-tolerance dosages and high-tolerance dosages is thus much less than 1 to 100.

http://www.erowid.org/chemicals/heroin/heroin_dose1.shtml