Thought I needed replacement battery, but maybe I don't. What's going on?

[Anonymous user]

Recently my computer system went down despite being connected to an APC Back-UPS RS 1500 LCD, and it didn't even seem like there had been a power hiccup in my home. The Back-UPS immediately started beeping, the display showed the flashing "bad battery" icon, and I believe the screen also visually showed that my battery was depleted (empty graphic battery icon). I muted the alarm, and proceeded to operate my computer in "online" mode realizing that my UPS was no longer going to help me out in the event of a power outage. I checked the display a number of times following this event, and it appeared that my battery was still empty/bad. Since the unit is four-and-a-half years old, I decided it was likely that the battery was indeed past its useful life, so I ordered a replacement battery. However, it's a few days later and there no longer seems to be any indication that there is something wrong with the original battery. The "bad battery" icon is gone from the display, and the graphic battery icon appears to be "full." The only thing that may indicate a battery due for replacement is that my "estimated run time" is only three minutes while my load is only 24%. That seems like a shorter run time duration than I remember. Can anyone shed some light on what may have happened? Does this sound like something that happens from time to time, and if so, why? I just received the replacement battery yesterday, but now I'm wondering if I need to replace. I don't want to replace the battery if I really don't need to yet. Thanks in advance for any info about this.