It would be a great "Setting" to choose to have myHeritage automatically email you a GED archive at the end of the day (if any updates where made to the site). I would suggest this only for paying customers, to encourage people signing up, but also to minimize the load on compiling them. Since you have sites all over the world, the compiler would probably be running 24/7 and launching emails around the clock.
Most sites don't update every day so, they wouldn't be emailed. Just the one's that have changes made to them AND where the webmaster has chosen to receive these special archives.