I use one 5000mAh LiPo, top it up after each round. Obviously, that will need to be replaced faster than in a two-lipo set-up (it will have double the use than two LiPos), but they will still get the same number of cycles each.
LiPos are not affected by being partially charged/topped up continually - thankfully we are past the days of NiCd and NiMH.
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