Summoning skills up faster if you are using your BP's on appropriate level targets. Cast/release is not meant to be the primary means for skilling up.

If you are actively using your avatars in something like besieged (Bosses, to a certain point) or abyssea xp parties, it will skill fairly steady. Alternatively, you could go somewhere like Dangruf Wahdi and do the top level GoV mobs (crabs/monkeys can give good skills to 95 or so, higher if you have the patience).