Hi and welcome also. First off sorry about the loss of your dad. Hope that continuing to have the cattle he must have enjoyed will make you feel closer to him.
We do not leave our bulls with the cows all year. We have 2 calving seasons, a spring group that calves Mar through May, and a fall group that calves Sept through Nov.. About 90 days each, and mostly because several places it is very difficult to get the bulls out except by bringing everyone in. 90 % of the cows will calve in a 60 day window and it does allow for the calves to be in a more uniform size, grouping, for sale. If you dad used to sell at about 9 months, then he was giving the cows approx 60-90 days of dry time before they calved again. If the bulls are in there all the time you will not be able to be as sure of making sure they get a proper dry off rest before their next calf. Since they are your cows, anyone that works for you should be doing it the way you want; and the way you are used to it being done at least for the present. Since you are getting your feet wet, I would think that you should do it the way it was done for a little bit til you get a feel for what you are doing. Leaving the bulls in year round is not a bad way; different strokes for different folks.
It is also a little easier to be watching them to calve for a defined time frame, to get the bull calves banded, and then when they are done calving, you don't have to be as intense on making sure they are okay. For me, it is just easier to be watching and recording all the calvings and then checking at pasture is not a twice a day thing. Plus this way we know that everyone is done calving and anyone that doesn't produce, usually goes to town.
I think it sounds like your Mentor is the one you should be listening to. If he knew your dad, he may be familiar with what he did and can help you to do the same. Once you get into it and if you decide to stay with farming, then you can make some more informed decisions as to what you might want to do differently, or to stick with what works.
You can Private message anyone and I am sure someone like gizmom will be able to help you since you are in the same general area and would know the climate, grasses, and markets down there.