IMO, levels depend almost entirely on pacing:
How long are you going to be playing that character?
How many sessions? How often are you going to want to level up?
How many fiddly bits will the level contain?
If you're only playing one session, after which you either expect your character to be dead, or expect to swap characters, you only need one level -- the level everyone starts at. This could be Epic already (first level, 300 hp and +20 to attack rolls), if you want. The point being, you're not going to progress that character in power at all, so it doesn't matter.
If you're playing, say, for 3 months, once a week, after which you expect your character to be dead or to get a new character, maybe you have a spread of six levels, so you can level up every other session. Each level might contain a new ability, so you get six powers over the course of your character. Start in January, by March, you're playing something new.
In 4e, if you want to see all 30 levels of any one character, and you level up about once a month you will need to play, on average, over two years.
That's a bit long to play any one character for, IMO, so I think the level range needs to be brought down.
I'd like to see everything a character can do in a single year, leveling up about once a month (which might be every 2-3 sessions). So maybe 12-15 levels.
FFZ has 12 levels for this very reason. Your campaign should take about a year. Then, you get to have a new character.