I'm a little late to the discussion, but thought I'd add my 2 cent. I definitely recommend a tender for any low use vehicles and am a fan of the NOCO brand ones. They are a great addition as long as you think to plug them in.
The 2000 F-250 7.3L is bad about going through batteries, largely because it sits a lot, and it's got two big (relatively) expensive batteries. I don;t drive it every week and if it sits more than about three days it becomes very hard to start. At this point I'm pretty certain that I've got leaking injector o-rings letting the high pressure oil rail leak down. If not plugged into the tender between drives it can easily drain the batteries while trying to get the rail filled back up and pressurized. Plugging it in doesn't help with the leaking issue, but the batteries do stay charged long enough to actually start the truck. On the last set of batteries it also seemed to help pro-long their life, can't really say about this set because I neglect to plug it in a lot of the time and it'll be moving to the next owner in a few weeks.
Also works great as a small portable charger (corded, but small end easy to move around) that I easily can stick on any of the batteries if needed. The F-100 is another of the low use vehicles, only leaves the yard a couple of times a year. Regularly stick one on there to charge up and move it around the yard. Will be getting one of the 2A onboard chargers and installing on it permanent. It's hopefully going into the shop to start a rebuild/resto next year and will get used a lot more after, but it'll get plugged in most of the time it's not used to keep it ready to go. Between a fresh engine, transmission upgrade, and some AC it whould be a lot better to drive year around. The last part is why it sits a lot now. It sits for an extended period and it needs work. I get it up and going then the heat hits and it sits again. When I was younger, I didn't mind the no AC thing driving a first gen Ranger. These days if it doesn't have AC I'm not driving it in the summer heat, around here that's most of the year.