DI and DII have limits on training, but not too crazy of limits
DIII has a more strict and lower limit on training, meaning they have X number of hours they can practice and such.
NAIA has no rules they can technically have full full practice every day of the week.
Someone that likes to read rule books can give you more details on the time commitments.
They all have some rule in place of being on the mat though. You can have "pre season" training.