It is a GEL battery that more stable and last longer than normal other batteries.
It should be charged back fully regularly to prolong its lifetime. Eg, once fully charged back in a week or even in 10 days time. To do this (fully charge it back regularly) right, the battery will serve you in good condition for years.
Do not always use it till it becomes empty. (It will cause user damage.)
Do not always use it when it is just charged little. (It will cause user damage.)