my basic plan is to run about 1 encounter per daily :-p. I will probably add 1-2 encounters in there but they will be "easier" encounters. 1 per daily of encounters that are actually hard .
Not always optimal--see the rules on milestones. There are definite rewards in the rules for going through multiple encounters in a day, especially multiple encounters without a rest.
usually, I'm aware of the milestone rules. You get an action point which is once per encounter anyway. I plan on each challenging encounter eating a daily power. I guess I should explain this better. I mean that challenging encounters (party level +1-3) should be eating dailies, so I'll have ~1 of those per daily the players have, otherwise they will just save them up and crush what should be a tough encounter :-/. I define these slightly differently then the DMG so here is what I think of them as.
Easy encounter: (party level -2 or lower). Doesn't count towards a milestone, the party just beats it up.
Normal encounter:(party level or -1 level). Counts towards a milestone, shouldn't require a daily power from more then 1 character, if even one most of the time, maybe an action point or 2, but not hugely resource draining.
Challenging Encounter: (Party level +1 or +2). most characters will pop a daily, and probably half of them will toss an AP.
Hard encounter: (party level +3-5) These are hard, they are major quest ending fights. I don't expect I will use +5's often, unless I have an optimized party and/or it's their ascension quest. I fully expect everyone to use an AP, and probably 1-2 dailies if they hope to survive.
The DMG refers to +2 as a hard encounter. +2 encounters can be lethal to a player who makes a poor decision, but it's unlikely that a TPK will occur. That isn't hard by my standards. Hard means that one character is likely to die, and everyone will be expending resources in a major way. if you play poorly (such as splitting damage amongst the targets) a TPK is likely. Despite all of this, I almost never use hard encounters, and I have had very few TPKs in my time DMing. I have given out some hints though "these look like challenging foes, you might not be able to hold back".