In games that use level-up system with team members and/or beings that become your allies(like Pokemon and Shin Megami Tensei for example), do you think that all members should always be at the same level and level up at or close to the same time as everyone else? or should they all be at individual levels and get stronger at thier own pace?
My opinion is they should always grow evenly, and possibly even join your at the same level as you or the majority. Especially if you have more team members in the game than your allowed to bring with you in battle, all inactive members should gain the same amount of exp as the ones active, so if you have a change of heart or need to switch to them because of thier stats or elements, you can do it without worrying about them surviving :)
An idea I had at one point was a game where the whole team links themselves together so they all default to the level of the main character and grow at the same rate(their stats and element weaknesses/strengths are still the same though) and each person can send thier exp to inactive members, like telepahtic twins! :)