Love your thinking Doc,
Yes, freshness.
I must say that since going all grain, and using kegs, drinking beer that fresh is lovely.
Since you inspired me to get a filter, its even better. I've filtered 2 kegs now, and loving the results.
I made a light beer which I filtered and kegged Thursday afternoon, force carbonated until one of my arms actually did fall off. On friday morning using my remaing arm, i gave it a good shake again, then backed the pressure off.
On Friday night, I sampled this light beer (3.5%), and it is bloody beautiful.
The keg is now only 1/2 full, unlike me who got quite full.
My point is, the beer was really nice after only 1 day out of the fermenter.
This beer could possibly improve with some age, but I am quite happy to drink the beer that fresh, it really is nice.
It might also lose some of its freshness over time as you say, so for now, I'm getting into it fast, its not worth the risk
Will post the recipe, even though its really basic...
Cheers,
Chris