A portable battery or battery pack is one which is sealed, can be hand-carried without difficulty, and is neither an automotive nor industrial battery.
How long will a portable battery last?
Before you scroll down to search for the short answer, here it is: most power banks will last, on average, anywhere from 1.5-3.5 years, or 300-1000 charge cycles.
Is a power bank worth it?
A power bank on hand is an ideal backup to recharge or top off a device when you are far from a wall outlet. These power banks are good for just about any USB-charged devices such as Cameras, smartphones, GPS systems, Gaming Devices, Laptops, GoPros, MP3 players, and even tablets.