Again, this is something to be decided between the mentee and mentor. Your initial conversation would be a good time to discuss the time and effort the mentor could realistically make. You can take a view if this is inline with your own expectations.
We would stress, however, that you as the mentee should take the proactive role in the partnership. While your mentor will get a lot out of relationship, you and your goals should drive it.
It’s also important to have a flexible attitude. There may be times, for instance, when your mentor might introduce you to someone in his or her network who might be better placed to help with a particular situation.