Long term beer storage?

What is the best method to store home brewed beer long term (several months)? I brew a batch of beer in march I set four a side in a closet that usually hovers between 68-72 degrees. I just cracked one open and it had a sour kinda spoiled milk after taste. The beer tasted great when it was brewed so this is a definate down grade in flavor. So my qestion is.. Do I store it in a cooler place, in a fridge, or was this just a freak occurence? What is the best long term storage method? Everything I've read and heard say tha long term storage should increase the flavor.

a fridge will "lager" flavor out of the brew.

I have stored at 65F or so in my basement for 2 years on a low gravity brew, no problems.

Oxidation is probably the biggest factor regardless of storage temps. With good habits as far as that goes, beer will last indefinitely.

Ditto.

Best way to store beer is probably a well sanitized keg at fridge temps. If you're looking to age beer, then I would go with a well sanitized bottle at 55f or so.

When you're looking to go long term sanitization is very very important. Sour flavors would indicate infection. Also you want very little oxygen. Either bottle condition or counter pressure fill from a keg.

As for your beer, I would crack another maybe it was just one that evaded the PBW and star san. If you don't need the bottles you can let it sit longer and keep your fingers crossed. But I would go a bit colder for sure.