Job rewards

I was wondering if there is any advantage to upgrade a job if it doesn't give access to a new circle of abilities ?

Actually, if I am not wrong, units get access to new abilities at least at level 3, 5 ans 8.

So, if we have enough job materials to upgrade a job at level 7 for example, but not enough for level 8, is it worth to do it, or is it better to actually not spend theses materials ?