Aging beer is a big, broad topic, but today is solely focused on the vertical – compiling different vintages of the same beer and cracking them open at the same time. If you shop exclusively at the LCBO, the vertical is very hard to pull off. It requires access to the same beer every year, which is rare due to the LCBOs ever-changing seasonal release program. The same beer might appear for two years in a row, like the Brooklyn Double Chocolate Stout, only to disappear and possibly never return again. There isn’t a hard rule, but you probably want at least three vintages to be able to pull off a vertical tasting. Consecutive years are not required, but are always nice for reasons of symmetry.
Three years ago I decided to start stockpiling for a vertical using the Mill Street Barley Wine. It was a local beer that was pretty much guaranteed to be available on a yearly basis. The swing top bottle was a little worrisome for the purposes of aging, but it was a risk that seemed worthwhile, even if just to decide that this type of bottle was useless for aging beers. Buying the bottles is, in many ways, the easiest part of completing a vertical tasting. The hard part is forgetting about the bottles and not drinking them over the course of three to four years (or more if you have the practiced patience of a Buddhist monk). Three years was as long as I could go (these aren’t cheap bottles, after all), so let the vertical commence!
Obviously with a vertical of high-ABV beers, you need some friends to help with the arduous task of drinking the beer (once again, usually fairly easy). They also might have bottles themselves and be able to expand the tasting. My preference is to start with the oldest bottle and move up to the most recent in case the recent vintage is too fresh and brash, but it is fine start young and work backwards through time.
The three year vertical of Mill Street barley wines was a pleasant surprise. The 2009 bottle had really rounded out and had an amazing depth of flavour. No sign of oxidization or any issues from the swingtop. The version from this year was still fresh, hoppy and boozy, which I quite like in a lot of barley wines. The 2010 was somewhere in the middle – still some rough edges that hadn’t rounded out, but lacking the complexity of the ’09. Another year would have really made it really nice.
You may still be able to find some of the Mill Street Barley Wine around in some LCBOs or from the Mill Street Brewpub retail store to start stockpiling for a vertical tasting. It takes a couple of years of patience, but the end result is a funny and tasty night.
A Year Of Beer! 
I know what you mean about the will power required to not drink your aging beer. I got a few beers aging and at least for one of the Barleywines I am constantly wondering if I should keep ageing it or if I should drink it, and I only have had it for about a year. Maybe I start thinking about a beer I could try to do a vertical tasting with.