For members who smoke a number of bowls a day especially, deep cellaring is the way to go. Gauging how much of what is an art, but not impossible. If I bought no other tobacco starting today, I think at the rate I smoke, I'd be good for about eight years, with better and better aging leaf as I go. However, since I seem to buy more than I smoke, along the way, I'm not especially worried. Like most, I'd be pleased to live to 120 gently puffing all the way. Not likely but perhaps the best attitude.
OK so - math time.
The way I figure, I'm buying at an average rate of 16oz a month and I'm smoking at a rate of on average 2oz a month (sometimes a bit more).
I'm already acquiring at a much higher rate than my consumption (so I'm auto-cellaring, like you said with a nice age building up as I go). I tend to cellar blends that I 'try out' and probably don't dip back into them until months (or years) later. In 6-months I'll have an excess of 5 1/4 lb's, that's over 10lb a year.
If I carry on smoking at that rate, the excess 10lb alone will last me 6 and a half years. I don't know if I'd want to have over 20lb of tobacco in the cellar at any given time, but it's certainly protection against future difficulties.
Added to the above-mentioned risk of online sales disappearing (at some point) cellaring just seems like a no-brainer and I'm glad to be doing it.