Well, my Jubilee and Blink characters won't actually arrive in the story for some time, so don't feel rushed. It might also be good to save some characters for later on, in case any existing ones die or are otherwise written out of the story. For me, I will likely only have four active main characters at a time. Some of mine will shift into background NPC roles as necessary, or they may be temporarily written out of the story, such as when Thor and Loki go to the future or into deep space after the Battle of New York. 

Kindred, if you wanted to have older, more experienced versions of Professor X and Magneto, they could come back from the future with Thor to fight Loki or something. Once we get to that first instance of time travel, the initial "teenage rookie superhero" part of the story will have been thoroughly explored, so I am fine with older heroes coming in at that point. 

Also, just so everyone is aware, due to some switch ups at my job, my free time is going to be drastically reduced. As a result, I will only hop onto this site a few times a week. I have cancelled all my 1x1 RPs on here and the only one I plan to keep going is our Avengers thread. Outside of that, what free time I do have is going to be dedicated to writing my e-novel.