I did the same thing (Only on purpose) and used my grantable levels to make a level 60 of every single class on my main account. I don't ever plan on using anything other than shaman on my slave accounts anyway (though I have a 4 60+ warlocks and a 60+ druid as well on those), and this way if I stop multiboxing I can pick any class I want to play on my main account and start at 60 minimum.