Here is how I configured my system and the network shares never drop off when the MAC or NAS go to sleep nor do the shares drop off when I reboot.
1) Edit your auto_master file located in /etc
sudo nano /etc/auto_master
/NAS_Shares NAS_mounts
ctrl o
hit "enter" key
ctrl x
2) Create the NAS_mounts file in /etc
sudo nano /etc/NAS_mounts
Movies -fstype=smb smb://USERNAME:PASSWORD@NASIPADDRESS/SHAREPATHONNAS
Television -fstype=smb smb://USERNAME:PASSWORD@NASIPADDRESS/SHAREPATHONNAS
ctrl o
hit "enter" key
ctrl x
3) Activate changes to the system
sudo automount -vc
Try that and see if it works for you.
