I've got 15mh too,I withdrew my BTC a few days ago,it was only .04 BTC but went smoothly,no issues & on the first try,you sure you did it correctly
Not sure how you could screw it up,but you never know
I figure 3 months at least for ROI,maybe longer if the network grows faster than I calculated.........which I've been wrong before
BTW,the Zens look to be the most consistant high payout,waffle is up ATM,but it may not last
My main worry is,if they go under,all investments are lost.Hope they stick around for 3 more months at least