Depending on your machine you may never get the push.
https://www.macrumors.com/2018/06/04/macos-mojave-supported-macs/
While macOS High Sierra was available for some machines manufactured as early as 2009, macOS Mojave is largely limited to 2012 or newer machines, with the exception of some Mac Pro models. Here's a full list:
MacBook (Early 2015 or newer)
MacBook Air (Mid 2012 or newer)
MacBook Pro (Mid 2012 or newer)
Mac mini (Late 2012 or newer)
iMac (Late 2012 or newer)
iMac Pro (2017)
Mac Pro (Late 2013, plus mid 2010 and mid 2012 models with recommended Metal-capable GPU)
As you can see, compared to High Sierra, the update drops support for the older plastic MacBooks, and MacBook Pro, Air, mini, and iMac models from 2009, 2010, and 2011.