I've used charger/maintainers (hereafter referred to as C/Ms) for well over a decade, actually since 2006 (in the case of my drag race car, with two batteries and no alternator, stored between races), now.

For the other cars & trucks, it began when my wife had to drive mainly to school and work, while I would be 50 miles away (or more) at work or at more distant drag strips, racing. Didn't have time to waste if one failed to start, so we'd just grab a backup! So, we had two vehicles for her to use (commuter car and pickup), and three for me (commuter vehicle, dedicated tow vehicle/backup truck), starting around 2007. All had/have flooded standard batteries, except for the Optima Yellowtop AGM, which I installed in my home-built squareback trailer in 2012 (still works). The vehicle lineup has changed over the years, but my reliance on C/Ms hasn't.

I'm currently using five C/Ms:

• 1) two Amazon Basics 2amp on the two trucks, '98 GMC and '04 Chevy 2500HD,
• 2) a Battery Tender 1.25amp on the '01 X5,
• 3) an Autozone 1.25amp on the '09 HHR Panel,
• 4) a really old BatteryMinder 1.5amp on the trailer's AGM, and
• 5) 'just added yesterday', a Nexpeak 1.75amp for the new battery on the '98 Dixon ZTR3304 riding mower.

At first, all the batteries were lasting between 7 and 11 years (the AGM is now over 14, though), but a couple as few as 3 (X5 and mower). I' don't think the batteries are as good as before, but I am only buying AC Delco and Duracell batteries (made by East Penn Mfg., for Sam's Club) in the last eeight years.

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01 BMW X5 E53,3.0i-5L40E, 7/13/01
topas-blau,Leder-grau,"resto-project car"

Here:
14 Lexus ES350,3.5L-U660E
09 HHR Panel,2.2L-4T45E
04 Chevy 2500HD,6.0L-4L80E
98 GMC Sierra 1500,5.7L-4L60E

Gone:
66 Chevelle Malibu 2dr ht.,327>441c.i.-TH350>PGlide/transbrake
08 Cobalt Coupe,2.2L-4T45E
69 & 75 C10s,350c.i.-TH350
86 S10,2.8L-700R4
73 Volvo 142,2.0L-MT4
72 & 73 VW SuperBeetles,1.6l-MT4
64 VW,1.2l-MT4
67 Dodge Monaco 500 2dr ht.,383c.i.-A727
56 Chevy 210 4dr,265c.i.-PGlide