Well, my APC Smart 750 doesn’t do that well, but I am probably working it too hard and not enough cooling airflow.
It was bought (reconditioned unit but with new &AH batteries) and served a single NAS - a ReadyNAS Duo with 2x1TB, which became 2x2GB. The 2x1GB going into USB enclosures and used with an old Linkysys NSLU2 unit.
First set replacement batteries was March 2013 (so 3 years use), by which time there a new main NAS (ReadyNAS Ultra2+/Pro2 with 2x4TB then 2x6TB, a backup NAS (ReadyNAS Ultra2 with the 2x4TB and the original ReadyNAS Duo with was max’ed at 2x2TB.
Second set of replacement batteries was Feb 2016 with 9AH units (just under 3 years), by which point the UPS was in a cabinet with all the NAS units and subject to a lower airflow than before, but it needed to be tdied as it all couldn’t be hidden anymore, as a 4 NAS unit setip, with 3 RAID1 volumes (8-9 spinning disks).
Batteries had to be replaced again in Sept 2017 (18 months later) but the main volume now 2x8TB, baclup 2x6TB (2x4TB now used as off-line backup), but also powering the NUC used for ROCK.
Just replaced again in April 2019, again only 18 months later). Main volume is now 2X10TB, backup NAS has volume 2x8TB) and the 2x6TB now unused - must get an USB enclosure for those.
So expecting late 2020 to have to replace again.
Unfortunately, there is no further room in the cabinet for a bigger UPS and obviously limited air-flow, and the summer seem to be getting warmer.
In terms of alerts - no, no Email, just a red lead and a continuous beep.
I use ups-trader.co.uk and buy the cells, transferring the connector assembly - see https://secure.ups-trader.co.uk/17-individual-cells