Hmm...I just realized I never actually posted an answer here:
On CrazyBike2, I used to have about 350Wh usable, with the 36V SLA, 3x 18/20Ah, and that was about 45lbs, with around 8-10 usable Ah, IIRC.
Then I upgraded to a used 48V NiMH, 13Ah (more like 9-10 usable, IIRC), for something like 400-450Wh, for what I think was around 25-ish lbs.
Now it's a used/repaired 48V LiFePO4, originally 20Ah but now around 12Ah, and maybe 25-30lbs, I think (I'd have to weigh it again, I can't remember for sure). It gets around 600Wh of usable power before LVC.
For a time I ran both the NiMH and the LiFePO4 packs, and could switch from one to the other as needed, so the most I've had was about 1KWh on the bike at a time, I guess.
(there is also a 12V NiMH lighting pack on there, of around 8-9Ah usable, but I don't count that in the total as it's not usable for traction due to damage and sag; it's another 100Wh or so, at most, though).
Most of the time, I do not use more than 1/4 of the LiFePO4 pack's capacity, but there are reasonably frequent trips that do use up to nearly all of it; enough to justify having that much (even if it wasn't for the pack type requiring that much just to function as a traction pack for C-rate). It's also nice to not *have* to recharge every time I come home from work, as there are some shifts that are so close together I don't ahve time to do all the other necessary stuff, much less remember to charge the bike.