The early battery problems are more or less a thing of the past. Certainly the batteries supplied today seem to be much better than a few years ago. Don't just single out Alien take a look at the eZee battery failures and others (Flecc could probably give chapter and verse on this) it affected many suppliers with the early Lithium types. These suppliers worked hard though to address the issues...
Plan on a new battery between 2 and 3 years regardless, Lithium will degrade even if not used, although I note there where some posts a while back about a Ping battery still retaining near full capacity after 3 years...but typically capacity will have dropped substantially by that time and the battery will be due for replacement.
Plan on a new battery between 2 and 3 years regardless, Lithium will degrade even if not used, although I note there where some posts a while back about a Ping battery still retaining near full capacity after 3 years...but typically capacity will have dropped substantially by that time and the battery will be due for replacement.