First, is Jai Alai actually a hard beer to find? The Total Wine and More across the street from me has it by the truckload.
as Space mentioned, they have only recently returned to the area. they don't distribute at all in MD, and i haven't seen it in DC (not that i hit many shops), so finding some in Tysons this past weekend was nice. i haven't had any in at least a year, probably longer.
Also, is "how many days old my beer is" really a thing? At how many days does beer become sub-optimal?
the aroma and taste of hops drop off pretty quickly. for beers where hops are the main attraction (read: IPAs), it's all about the freshness. i generally only buy IPAs if they are less than a month old, maybe 6 weeks if stored cold (negative points for TJs: all beer is stored on the floor, so room temp). the alchemist brewery, makers of heady topper, will only distribute to locations that have on-site refrigeration. no warm storage allowed (not that the stuff requires much storage since it never lasts... a virtuous circle).
for most other beer, freshness is still desirable because beer stales. oxidation is mostly what you're trying to avoid. wheat beers tend to deteriorate relatively quickly, anything with dark malts (aka dark beers) tend to fare better.
and some beers benefit from aging. big beers like barleywines and imperial stouts might be too "hot" when fresh and need some time to mellow out. wild/sour beers with live bugs in them will continue to develop for years and become funkier, more complex, etc.