I would never let my Mac sleep. Let the screen go black but keep the machine up and alive. Waking up from sleep has been a problem for Apple over the years– sometimes machines won’t wake up at all, sometimes their keyboards/mice/printers won’t work, sometimes other problems. If you are connected to another machine (file sharing, or maybe a remote database) going to sleep will drop the connection, causing inconvenience at the least and maybe even data loss.
So do it my way. Go to the Energy Saver Preference Pane (Apple menu, System Preferences, Energy Saver)
and tell it you NEVER want the computer to sleep. Do what you want with the SCREEN sleeping (this will turn the screen black– in between, you’ll see the Screen SAVER, which is a different affair altogether), but DON’T set screen sleeping to Never. You don’t want the screen to show the same picture forever because it’s hard on the screen.