+ 0 Votes As mjd420nova said NickNielsen Moderator 2 years ago The units need to be exercised on a monthly basis and the major failure will be in the batteries.Most modern UPSs will automatically exercise themselves, particularly the enterprise-level units. They will also let you know when the batteries need replacing. A good battery (or set, in the larger units) should last three to five years. You can save money on the replacements by going to Batteries Plus or Interstate Battery. Both businesses will build the battery combination you need for your UPS at not much more than the cost of the batteries.