Sleep mode eventually leads to Hibernation mode which saves the current desktop into a file to 'load' when turned on. to put everything back the way it was. Sleep mode is only meant for a couple hours not 'while you sleep' (i.e. 8 hours).
I would just disable sleep / hibernation mode if this is a desktop. Click the power icon in the tray and select more power options > click on Hide additional plans and select HIGH PERFORMANCE. The go through ALL the options on the left side of the panel and set the computer to how you like it to respond.