Several years ago I ran tests using name-brand AA alkalines and 2500mAh NiMH
cells to power a STAX headphone amplifier. (This was not completely valid,
because I had no idea what the alkaline cells' rated capacity was. Does
anybody know?)

Much to my surprise, I discovered that the rechargeable cells powered the
unit as long as the throwaways. This means I'd break even after only 10
recharges. Even if I was off by 50%, I'd still need only 20 recharges.

The shortened life of fast recharging has to be weighed against the cost of
using throwaways. In practice -- particularly with heavy-drain devices --
you don't need many charge/recharge cycles to break even.

This is why I carry multiple sets of NiMH cells for my flashes and other
heavy-drain devices. With multiple sets, I don't have to worry about rapid
recharging, and can stick with 0.2C or 0.3C.