I never leave my packs in the tools, just because I'm OCD and like to keep them comfortably cool in my air-conditioned homestead. I'll usually put 'em on my charger for just a wee bit, 'till they just pass the 50% marker (I've got two of the super-chargers - the cooler looking ones that are all burley and show charging percentages), then take them off until I get ready to use them again. This way, they're semi-stored at a nice voltage, they're happier that way. When I get ready to use 'em, I'll slap 'em on the chargers again to top 'em off right before use.
I also remove them from my machines for safety. Just so nothing starts or drains without my knowing. Like if I left the light on on the mower, or if I left the trigger resting on something activating my trimmer ever-so-slightly. You gnaw'm sayin'?
If I were YOU, I'd mow, then leave them in that state, then charge right before using them again.
1.5 years with my setup. Batteries operate perfectly and I throw them in charger after using them and don't even look at them until I need them again. Run times have been a bit better in year 2. So I don't see the urgency about this whole subject.
I would not run the battery fully out, when your mower says low battery, stop and charge or grab a charged one. Store in a cool dry place and don't worry. You are supposed to have to worry. Look at all of your hand tools, do you worry so much about those batteries? These are lawn tools and the batteries are designed to "take it".
Just don't store them in a warm/hot place and that is about all there is to it.
This, in theory, SHOULD be better for the batteries. In reality, it likely makes little difference.
Heather, since Lithium batteries don't suffer from a memory effect, you're pretty much free to do as you please. The only thing I will caution against is fully depleting the battery (red light) and then letting it sit for long periods before charging. This has the potential to KILL the pack, since all cells discharge with time, and no cell is immune to the effects of an over discharged condition.
With your current routine of cutting three times before charging, I would recommend charging immediately after the third cut. I would think your batteries will live a long productive life that way. :-)