I was just starting up one of my worlds when my beacons wouldn't give me the buffs, I thought "Ok, new snapshot, beacons don't usually start up when a new snapshot opens." So I destroyed and replaced the beacons and put in my usual buffs. I then went a good distance until the buffs ran out, and my wandered to go back to the beacons. I then saw that I was a good 30 blocks away from the beacons, and they wouldn't give me the buff until I came like 15 blocks from them for the buffs to start up again.

First Picture: This looked normal, I was too far away for the buffs to start.
Second Picture: This was not normal, I was less than 50 blocks away, but the beacons didn't want to start up.

I don't know if this was a change for the radius of the beacons were reduced, but I have researched and saw no evidence of the beacon's radius for giving you buffs were decreased throughout the 1.9 Snapshots.