On the Mac there are a number of ways to control the sleep timers.  Some seem to work better than others.  For Mojave (MacOS 10.14.x) I have switched to using the command peset.

peset -g      shows a list of settings

peset -a       allows you to change those settings

Example:

bash-3.2# pmset -a sleep 120

bash-3.2# pmset -a displaysleep 120

bash-3.2# pmset -a disksleep 120

bash-3.2# pmset -g

Additional details on this are available at:
https://eclecticlight.co/2017/01/20/power-management-in-detail-using-pmset/