http://forums.kanoapps.com/threads/xp-bonus-from-assist-challenge-and-adventure.13944/ not my idea originally, please see this thread for the discussion so far on this topic
Been beat to death, You are not losing anything, ya have the same amount of times to click a challenge when there is no 3 day calendar, ya just getting something extra within the 3 Day calendar,xp coins and a reward item X 3 if ya finish all three.
Their reasoning must be, that it takes a longer time to find and help on 50 + 25 challenges until the Xp drops to 1, and with the 3 day calendars this could be done in minutes. If there would be a separate counter for the 3 day calendar, you could do an extra lvl with every 3 day calendar. When there is a 3 day calendar, helping on challenges its like walking on a mine field and I avoid helping on them until the Xp drops to 1.
I don't help when it drops to 1 cause I am not sure if that takes a spot from someone else who hasn't hit the limit.
I don't have the time to pick and choose which ones I help on. I click on every active link regardless of type or XP.