An attractive option for EA customers moving to Microsoft 365 E3/E5 is to buy the From SA User SL. As long as you have active SA on all of the desktop components you’re eligible for this cheaper licence.
If you have perpetual licences you retain the rights to use the desktop products at the last version (or any earlier version) when you transitioned.
The standard use rights of the From SA User SL don’t include the rights to install any newer version of the Office Professional Plus product, and for the last few years there’s been an exception that DOES allow this.
However, text in the October 2018 Product Terms (page 55) states that this benefit comes to an end for new or renewing customers on 1 January, 2019.
Download the Product Terms every month here: http://bit.ly/MSproductterms.