If you do resub to have a main account to manage everything off of, be sure to do a RAF for the 4 free accounts you use. If your time is limited, you can level to 20 really fast with the xp boost, plus have plenty of giftable levels for your main account if you want to boost a new char to 20 really fast to try out.

One thing to keep in the back of your mind if you resub to boost chars up, once your time is over you will only have 4 active accounts you can use. I know you said your time is limited, but if you do a resub for a month just to boost, you can try and get 2 groups up before your time runs out. For example, run Main account plus Free1, Free2, Free3, and Free4. Then after they hit 20, boost a new team with the Main account, plus Free5 and 3 chars from the other 4 accounts spread out however you like. That way after your time is up you will still have 5 chars to box with if you have an invite buddy.

Also if you wish to do BGs with your main and free accounts at 20, be sure to lock XP as max level free accounts are put into the xp locked bracket.