A good ratio for flight and ground is 1:1
40 hrs flight and 40 hrs ground.
Makes no sense practicing in the air what you don’t understand on the ground.
In an air conditioned classroom I have your full attention and in the airplane you have to juggle 5-6 separate items that require your attention and as a CFI I’m only one of those.
Ideally as a CFI your day is flight-ground-flight-ground in 2 hr slots.
Work 8 hrs get paid for 6.
That’s 75% efficiency which for a CFI is really high.
Instrument training at night makes a lot of sense.
Less cheating from under the hood, cooler calmer air and generally less busy controllers and different approaches you can fly.
ATC may allow a full ILS approach with procedure turn instead of radar vectors.
They may allow you to hold on the outer marker etc etc etc.
Another good one is landing practice for Commercial students.
Short field/ Soft field, full flap, partial flap, no flap, combinations of any of the above. Night gives you a different perspective.
Multi engine training at night for CPL ME add on.
Initial CFI training at night adds another difficulty element.