Also, just wanted to add that while the legal maximum limits for commercial wines are higher than what most home winemakers add, the actual SO2 levels in most commercial wines aren't much different than what we do at home. In fact, the move in the industry has been to reduce SO2 levels in recent years and with the increased use of inert gases throughout storage and bottling, most wineries have been able to keep quite low levels of both total and free SO2 since oxygen uptake can be better controlled. We tested some wines in my Wine Chemistry class recently and the free SO2 in both samples was around 30mg/l or ppm and the total was about 90 mg/l. You'd be hard pressed to keep them much lower than that at home, especially without the sterile filtration and microbiological analysis that commercial wineries use.