Every once and a while I come across [beers][1] that say they can be kept up to 5 years and become more developed over that time period, while [other beers][2] that are of the same style don't indicate this at all.  I know that some styles are defined by how long they can be cellared, but for other styles how do you know?  So my main question is:

**What are the main characteristics that differentiate normal cellaring period beers from beers with extended cellaring periods?**  Does it have to do with the amount of hops?  The amount of alcohol?  The type of yeast?

**EDIT:** In retrospect, this looks like it would be a good wiki question since it's more of an information gathering topic than a personal, concise question. 

**Here is a compiled list of comments made below as well as answers found elsewhere:**
<br>*Please feel free to edit this list (it is a wiki).*

**These are the characteristics that people have associated with good cellaring beers:**

 - Wild yeast beers
 - High alcohol content
 - Proper storage throughout the lifetime of the beer

**Styles of beers that lend themselves to cellaring:**

 - Lambic
 - Barleywine
 - Oud Bruin
 - Belgian Ale

**Characteristics that can develop throughout cellaring:**

 - Floral hop character diminishes
 - Hop bitterness diminishes, but at a much slower rate
 - Flavor complexity is developed
 - Malt character is developed
 - Can develop sherry and port-like characteristics

*Keep these characteristics in mind when selecting or designing a beer that you wish to cellar for an extended period of time.*

Here's a good [resource][3] I found about cellaring.


  [1]: http://www.gooseisland.com/pages/matilda/25.php
  [2]: http://www.harpoonbrewery.com/index.cfm?pid=143703
  [3]: http://www.brewbasement.com/featured/what-beers-should-i-cellar/