I don't think spending time leveling during the story is really needed. Just playing through will get you around level 40 by the end. I'm of the opinion that the game doesn't begin until after the story when you (me, anyway) start doing all the side quests, which are more challenging than the story. And by the end of the story you can easily level characters from 1-99 in just a couple hours.

A lot of people like to have that high level especially when they are fighting bosses and tough enemies..serves to boost the confidence.
Dustia/Negamuur or skeletons at Nabreus or Darklords later on..

quote RikuNova

I always keep characters at the same level. That way when yo are defeated in a boss fight, your backup characters can revive you.

esactly how i think of it, when you do a boss you need good back-up as well in case your good ones die

also levelling up isnt just about the actuall number or level, if you dont level up other characters they will miss out of Licence Points, someone said that you can have good equipment and crap levels, but you need licence points to get the good equipment, dont you.....

better to have very good all round characters i'd say, as soon as someone is a level above everypne else, i swap them for somoene with a lower level, to keep it balanced fpr bpss fights etc...

you can have very high 3 characters and beat boss very easily, or all 3 balanced, but struggle, 'cause other 3 dies by 1 hit, and they take 0 hp.

levelling the entire party to the same level is waste of time... in my first game i tried that and boy it was so time consuming and boring.... getting the entire party to lvl 99 is something that kinda annoyed me but back then i was really into the idea of having the entire party at lvl 99....... however in my second game that i started ... my main party is currently at lvl 89 while the reserve is at 51... my main focus is to get my main party at lvl 99... the reserve i dont know if i feel like levelling them too then i might do it but the chances of that are low... since it can be too time consuming.....