I'm an unlucky owner of a Samsung Galaxy Young (AKA Galaxy Y), a (very)low-end device. During use of this device I've faced some frustrating problems like phone that reboots automatically or network connection disappearing until you rebooted it. Adding the ridiculously short battery life it was just unusable.
I've looked for a solution to the problem, and found it in the "Use only 2G networks" option, that can be found under "Settings > Wireless and networks > Mobile networks". Now I have no more reboot or network problems, and I count stand-by battery life in days, not hours! If you haven't got a data connection, or if you are OK without a 3G one, give it a try!