Alright so here's why I think exos comeback took so long:

 

They first started telling us to wait for it back in September last year, right? Now if you count September and may, that's nine months we've been waiting... So then they were obviously meant to comeback in September, but then one of them got pregnant and they all had to wait for the baby to be born before they could have a comeback. My bet is it was kris that was pregnant, because that would explain the time he went missing (for a check up on the foetus) and the baggy old woman clothes he wore through the airport... Maternity clothes!

 

Looks like ace will have a brother or sister...^^