when to start boosting?

[The Rupt Brothers]

Boosting RAF alts with my main (Feral tank and MM Hunter for ZG) and doesn't take long.

1-10 low lvl quests
10-20 SFK (park the alts at the front door gates, and clear all the way to the boss. This helps not reaching max instances / hour)
20-40 SM Lib (clear first open area, park alts at the east arch and clear to the boss), SM Arm (same as lib then park at north arch, clear to Herod and pull him to the door so he gives the xp as well :P ), SM Cath (clear the first hallway and park toons on north wall near the arch. This gives xp when pulling Mograine to the door. Normally I kill most on east side when going up and west side when the cathedral is cleared to speed things up).
40-45 ZG I just speed kill everything with my hunter
45-59 Scholo (let my alts stand where they are when they zone in) drop down to the zombies, ghouls and AoE everything I can find. These lvls are the fastest imo. Level to 99% of the level then give the level.
60-62 Hellfire quests (I avoid collection quests as much as I can)
62-64 Zangarmarsh quests
64-66 Nagrand quests
66-67 Blade's Edge quests
67-68 Netherstorm quests
68+ WOTLK

[Zub]

that's pretty much what i do, with the exception of 55-60
i also do all dungeons at least once while in outland

Boosting RAF alts with my main (Feral tank and MM Hunter for ZG) and doesn't take long.

1-10 low lvl quests
10-20 SFK (park the alts at the front door gates, and clear all the way to the boss. This helps not reaching max instances / hour)
20-40 SM Lib (clear first open area, park alts at the east arch and clear to the boss), SM Arm (same as lib then park at north arch, clear to Herod and pull him to the door so he gives the xp as well :P ), SM Cath (clear the first hallway and park toons on north wall near the arch. This gives xp when pulling Mograine to the door. Normally I kill most on east side when going up and west side when the cathedral is cleared to speed things up).
40-45 ZG I just speed kill everything with my hunter
45-55 Scholo (let my alts stand where they are when they zone in) drop down to the zombies, ghouls and AoE everything I can find. These lvls are the fastest imo. Level to 99% of the level then give the level.
55-60 Ramparts
60-62 Hellfire quests (I avoid collection quests as much as I can)
62-64 Zangarmarsh quests
64-66 Nagrand quests
66-67 Blade's Edge quests
67-68 Netherstorm quests
68+ WOTLK