The 70 battles are not correct, in every case if you take this at a daily basis. If you start at 100% you need 70 battles to reach 50%, but if you play the next day (let's say after 24 hours) your ECR will by arroung 74% and you will reach the 50% ECR after 39 battles, so you cannot do more than 39 battles a day without to reduce ECR under 50% if you play only once a day. I really cannot imagine that the splinterlands-team is not aware of this fact. Absolute Maximum is 48 battles a day when you submit a battle every 30 minutes. If you play 70 battles a day it is not important how and when you play you will be latest at the 2nd day significant under 50%.