I think you should have at least enough crew endurance for 5 days, because you don't want a morale hit interfering with accuracy just because a 5-day turn processed at an inconvenient time.
That is some serious stand off range on your missiles. Unfortunately, late game, long range missile fire is effective against civilian shipping, and that is about it. You need such a huge throw weight to get through AMMs that you will waste a lot of missiles on overkill. You should at least have a sensor on board that can retarget against ships of 200 HS and larger.
Part of the problem with long ranged missiles is you can't do it half-assed. If you don't have enough missiles to kill the majority of the enemy fleet in a volley, you are being inefficient, and might have to retreat to reload.
Also, if you had some fighters with anti-ship fire controls and launchers and others with anti-missile fire controls and launchers you would be spending less on fire controls, and have faster, more efficient strike groups. Fire controls are EXPENSIVE in late game.
You are also getting to the tech level where cloaked warships are going to have smaller cross-sections than fighters, and more space for fire controls for outranging them. Plus more space for ECCM and ECM.
That said, there IS a late game role for fighter bombers in late game. You can use them for colony security, for taking out probing survey vessels, buying important time for the rest of your fleet to show up.
Missiles are great in low tempo games, where you have years between wars to build up missile stocks. They are great in that you don't have to pay maintenance on a planet-load of missiles. But even when you win, you have thrown away a tenth of your build cost in those missiles.
As an RP, where you might have artificial limitations in the size or cost of your fleets, but no limitations in your missile stocks, it is GREAT. Having RP issues driving your fleet design can be FUN.