why do people use infinite and unlimited interchangeably?
edo's don't have INFINITE chakra. INFINITE means constant spamming, never draining, never needing to recharge.
the ego's have unlimited. Meaning their chakra supply is used but is also recharged over a quick amount of time, not that it's never depleted.
OT: the question you poses plays in part with the notion of chakra period. if you really think about it, chakra never runs out, kind of like energy -- it just takes time to recharge or reaccumulate
all Edo does is use this same notion but its just on fast forward. the time it takes for an edo to recharge their chakra when compared to a mortal is much much faster hence why it appears as if they have unlimited
technically speaking, everyone has unlimited chakra. you can use chakra as long as u want just as long as u allow enough time for it to recharge.
to draw an analogy, think about how your character in a video game heals on its own, like in Call of Duty or Halo -- you can die if you are shot too many times in succession (chakra usage), but if you're shot once every 10 seconds, you'll never die because you're allowing enough time to pass to be healed (chakra recharge)