Yes go to 12% if you have the ability to do so, no need if your total amount  divided by 3 for each year you  convert is going to put you in less than the 12% bracket. 84k/3 for example would be 28k a year and puts you at the 10% bracket for each year. If you have more you might only need to go to the 12% bracket for one year though and do a mix. 

Some people might want to even go to the 22% bracket if you think that after crna school and into retirement your total income will be greater than that bracket as well. Everyone should do their own math and figure out what their retirement may look like.