They could have just had you gain an action point each encounter, but not for the first encounter each day. Wouldn't that work?
The problem with giving out twice as many action points (minus 1, in the case of this suggestion) in a party full of paragon-tier warlords, is that every time someone uses an action point, all of the other warlords give him bonuses
that all stack!. In addition, at paragon, everyone gets their own bonuses for using action points, as well!
This typically meant (in my game), that they would pick the two or three enemies most likely to have interesting abilities and make sure they never got a first turn.
Just adding more monsters would have increased the difficulty, but I would have had to decrease the XP awards, if I wanted to keep them from skyrocketing through the levels (and this group would have rebelled, if I had dropped the XP awards).
All that said, I do like what milestones were meant to accomplish--I just think the bookkeeping made it tedious (especially if the party does not take an extended rest in between sessions).
One thing that might work to help extend the adventuring day without making all of the encounters so easy to walk through would be to have the action point recharge whenever the PC misses two attacks in a row (but still only allow one action point to be used per encounter, of course). This would help mitigate the grind-factor of low dice rolls
and provide long-term endurance to the party, without over-powering classes (the warlord) that reward action-point usage.
And, it's easy to track. It might
seem like more to keep up with in the midst of combat, but I suspect that
every player remembers when they miss two in a row.