Chris suggested that I should look at the Mac app FruitJuice as a way of monitoring the battery usage on my MacBook to get a better idea of what is happening when I use the timer on it.
First of all, it's $9.99. That made me squirm. Then I remembered all those early years when software cost $40 to $250, and realised how my perceptions have changed when I find a $10 app feels like too much money. I did my reading, and it seemed interesting enough, so I paid my money and installed in on my MacBook Air. I didn't want to put it on the MacBook yet, I wanted to get a feel for it.
Bought it in the Mac App Store, and got it installed. Ran it, and set it to run at login time. First thing it did was tell me it wanted to do a Maintenance Run. Told me to plug the charger in and get it up to 100%. I did that. Then it told me to take the charger off, and run the Mac till the battery went below 20%. I did that. Took a few hours. Then it was calibrated and it knew what it was doing.
Now, whenever I use my MacBook Air, the FruitJuice app tells me how much time I need to spend on battery power each day. And right now, it tells me to spend one hour and five minutes on battery. This is good information. And it gives me plenty of other info about the state of the battery and my pattern of usage. Neat. I suppose it's worth the $10. If it keeps my battery running for longer before I need to replace it, and optimises the lifespan, then it is worth it.
So with all this info and practice done, it was time to put FruitJuice on my MacBook that is driving the Drobo and BackBlaze, the MacBook that started this whole exercise.
Oh. Rats. That MacBook is locked in at Lion, and FruitJuice will not install. OS is too old. So much for that.
But it's still useful on the two MacBook Airs which are both on the current OS.