1.45 diving time is not bad at all. Mines are around 1.30, will push 2minutes barrier this summer (hopefully).
If you manage to get 1.45 i am sure you can increase it by diving more frequent since probably you know much of the basic stuff.
I have friend, he is the deepest in the island (i belive). He does 3.5 minutes dive. Aspetto at 35 meters...No need to say i feel pathetic when i see him doing that. But he is a swimming instructor in university and he spent every single day in pool if he is not spearing.
edit: By the way he does all of those diving after 4-5 hour son stop surface swimming to reach the spot from the shore
