An encounter power is a power that cannot be used more than once per encounter. Getting a "once every other encounter" effect with a daily power would take some fairly complicated wording. Also note that this effect can happen many, many times in a given day if the party goes through a lot of encounters.Just seems to me that if it works the way you describe (and I'm not necessarily saying it doesn't), it would be more fitting as a Daily Power instead of an Encounter Power that can't actually be used every encounter.
My point is that it shouldn't really be an Encounter Power if it is not actually possible for it to be used each and every encounter.An encounter power is a power that cannot be used more than once per encounter.
Well, my first thought was that these powers didn't overrule the once per encounter rule. Somebody however pointed out that the wording says you HAVE to spend these actions points by the end of the round. This could imply that you have no choice in the matter, and that it's a matter of the specific overriding the general....normally you couldn't spend a second action point but this power is not allowing it, it's requiring it.
My point is that it shouldn't really be an Encounter Power if it is not actually possible for it to be used each and every encounter.
As for your assertion about using it every encounter and holding on to your normally accumulated Action Points, to what purpose? You lose them all when you take an extended rest, so there is no point at all in hording them, as they serve no purpose. And if you use them in an encounter, then Archer's Glory is useless for that encounter, or any encounter where an Action Point is used.