The double rewards only last for one day. Refer to this page for when the x2 and x5 days occur:
http://poolerino.com/eaccountdown/On the extra reward days more miners jump onboard so the profitability stays roughly constant.
Yes, EAC is
equally profitable as any other regular 10k/block day.
So why are they jumping

Because the profit-takers 'think' it is more profitable... it will only be profitable when everyone has forgotten about and the die-hard EAC miners are the only ones mining... no matter the block reward.