It takes me about 6 times to fully train a spell with 50 int. It always takes me 2 times to fully train a spell with 35 int.

Why?

What class, gen, remort class, and level?

gen 10 mage, gen 10 knight doesn't matter keep your intel in the low to mid 30's and you are fine

Exactly, I used Deneb. Gen 10 Mage. Trained with 50 int and it took an average of 6 times to fully train something. Then I removed equipment until I was at 35 int and it always took 2 times to fully train.