how long will beer stay fresh in a kegarator?

As long as you keep is under pressure it will not go flat. Beer spoils depending on three factors; temperature, oxygen and bacteria. If you keep CO2 pressure on it bacteria can not get in. If you keep it cold it will stay for a very long time. The beer in the lines may go bad, but its highly unlikely the beer in the keg will.

You can do this with bottles of beer but they can go "skunky" by being exposed to light. It is from the left over enzymes from the hops reacting in photosynthesis. A keg is made of stainless steel, and does not let light in. Keg beer does not get "skunky" unless there is an infection in the dispensing lines. If this ever happens remove the lines and clean and sanitize them.

That being said most light beers can last 6 months without any noticeable change in taste or quality. Most dark beers can last 8 months.

Its kind of like any food that can stay fresh unrefridgerated (like applesauce). It has preservatives (sometimes natural, sometimes artificial) but it will spoil eventually. AKA "skunk beer". If it is unopened beer should be ok for about 100 days. It might be good longer depending on the brand, but 100 days is a safe bet.

it depends how fast you drink it. I bet it could last a few months and still be good. I mean, the beer is remaining carbonated and refrigerated so youre pretty good. Hell, it could probably last longer. IT wont go flat as long as you attach the CO2 tank and make sure its always good.