Well we are some what in the dark as we do not know what the number of turns you are at. If it 200 that is one thing, if its 300 that is another.
So where are you on the tech tree. Do you have phasors or disrupters, are you creative or not.
What is the level of the game and how many races were in it? Prewarp start? This will impact how long it takes to get all the others done and head out.
In the main it does not really matter when you go as the size of the fleet is smaller when you go sooner and larger as the game drags on. If I have Anties in the game I am not going to go after them until I have dropped all the other out, but one planet, unless I am bored and want to stop. Either way I will have a fleet that will wax them. I like disrupters on BB or Titans (I usually do not have them). If I have Doom Stars I will have 1 converter to destroy planets and the rest dusrupters. I tend to refit when I am get down to the last last 10 turns before going.
Post a save if you want.