Hypersmurf
Moderatarrrrh...
Artoomis said:"...To succeed, you must make a Will save (DC 10 + the animal’s current HD, or the HD the tree will have once awakened)..." There is an obvious buit-in limit here - considering that you'll need an natural 20 before long, AND it takes 250 XP each time.
That's where the Mysticism Domain (from a level of Contemplative) becomes important.
Casting Maximized Awaken gives you +3 to Charisma each time you Awaken, which gives a +1.5 to all your saves via the Domain power.
Now, your saves are increasing by +1.5, and your Hit Dice are increasing by +2... but it hasn't been addressed yet whether or not you gain Skills, Feats, ability score increases, BAB, and Saves for that increase in hit dice. 3.5 made an effort to be consistent about those - they're based on hit dice.
So, every second Awaken spell gives you an ability score increase, which you can also put into Cha... and Magical Beasts have a Poor Will save, which means every three hit dice gives +1 to the Will Save.
So, for every two Maximized Awaken spells, you receive:
+6 Cha (direct effect) = +3 Will Save
+1 Cha (ability increase) = +.5 Will Save
+1 1/3 Will Save (Poor Save)
For a total of +4.83 to your Will Save, and only +4 Hit Dice. Your Will Save not only keeps pace with the increase in Hit Dice, but actually gets easier the more times you Awaken yourself

-Hyp.