This can be confusuing, so just to be really clear:

Your elite is valid to april 2015, that means you can:

requalify with 25000 miles up til april 2014 or 37500 up til april 2015.

No matter which of the above you do, the next requalification period starts in May 2015, where you can requalify again with:

25000 miles up til april 2016 or 37500 til april 2017.