To determine how many AA's you need and at what level you need to earn them, you need to ask yourself some questions.
1. Are you able to face the mobs you want without feeling totally overwhelmed.
2. Are you working to reach a level in your guild where you can participate in guild raids.
3. Are you a class that depends heavily on melee or casting skills
4. Are you a 'standard dps' class or a 'critical' class?
5. How difficult is it for you to find groups?
6. Do you prefer to solo or group or raid?
a. If you are feeling overwhelmed you may need to get better gear or more AA to handle the mobs you want to face. Waiting until you are a higher level wont be acceptable because when you reach a higher level, your friends wont want to hunt those weaker mobs. If you are doing just fine against mobs with zero AA at lvl 70, then hey, keep exp on full and skip AA until lvl 80. You will be able to find groups and experience much more of the world and will be able to avoid the long hours exp grinds in boring zones by yourself or with a partial group.
b. If your guild hunts in zones/instances with level restrictions then you must simply forget all about AA until you meet those restrictions. You dont want to be sitting in some Kunark zone all by yourself, grinding aa's, while the rest of your guild is taking down raid mobs and having a ball. Get yourself to the level needed so you can join the fun. Gear and AA's will naturally come later.
C. If you belong to a melee class, especially tanking classes, then some offensive and most defensive AA's are a must to survive. You may end up limiting your group because you can't tank the mobs they want to fight. In this case, you may consider getting a few aa's at earlier levels and gradually building your total as you level. This depends on your role in the guild also.
d. IF you are mostly a 'standard dps' class, or even more so, a dps casting class; then you can wait to earn AA's after you reach lvl 80. Your guild is depending on you to cast the correct spells and have the correct pets, and they could care less if you have some odd foci that works on lvl 65 spells or not. Your guild mates need you at the correct level and casting the correct spells in order to beat that raid event. Dont sit at a lower level grinding aa's and sitting on the side line during all guild events. However, if you are of a 'critical' class, then your guild is depending on you to fill a role, and if you dont have enough AA's to do the job, they will ask someone else to fill the role or maybe even ask you so sit out a raid to make room for someone with more AA to do that 'critical' job. Ask your guild class leader for advice on this one.
e. If it is difficult to you to find groups, it may be two different reasons. One, because others have grouped with you and find you undesireable. Two, because there are very few others around your same level and you simply cant find a group. The undesireable thing is easy to diagnose. IF you are snotty or whiney or greedy, then ppl will avoid you. If you are very poor at playing you class and are in-attentive and slow to react, then ppl will avoid you. If you are severly undergeared and under-aa'd then ppl will avoid you. So if when you do find a group at whatever lvl, do you constantly need a rez or constantly soak the healer's mana? It is not as simple as some ppl say when they comment that you 'must' have xx number of Aa's to be a good player at xx level. That is a cheesy cookbook remark. More often than not, how you play, how alert you are, and how you follow instructions, make much more of a difference than how many aa you have. Group and raid desireablilty are much much more heavily influenced by your playing than by your aa count.
f. If you prefer to solo, then you must maximize aa's at every opportunity. I am not saying get 2600 aa before you reach lvl 52, but you know what I mean. You will need to constantly split exp with aa exp at every level available. On the other hand, if you constantly raid, then you must get yourself to the level of the other raiders, (80) at your first opportunity. I have seen, over and over again, ppl being passed over for critical raid roles, simply because they decided to work on aa's instead of getting to the higher level as their top priority. Your raid needs the higher lvl pets and higher lvl spells. They dont need you to have 100 more aa than last month, but sitting 5 levels below every one else.
In some guilds, people who do this may cause others to wonder "what's wrong with this person? How come he cannot get to the next level? He got invited to exp grind in SHIP while farming cores this week but hes still at xx level...whats wrong? What, he wants more AA first? What is he thinking????" In other guilds, members are more focussed on the most efficient development, which means acquiring AAs at the lowest level that they are available, since they accrue more easily at lower levels.