Aliens

Case 1: Enter ranch early
It takes x frames to reach barn shooting position.
It takes y frames to kill aliens.
After, it takes z frames for it to turn 3:49am.
Total time in ranch: x + y + z

Case 2: Enter ranch perfectly
It takes x frames to reach barn shooting position.
It takes y frames to kill aliens.
You kill the last alien at exactly 3:49am.
Total time in ranch: x + y

Case 3: Enter ranch late
It takes w frames to go off path for activating timestop.
It takes x frames to reach barn shooting position.
It takes y frames to kill aliens.
You kill the last alien at exactly 3:49am.
Total time in ranch: w + x + y

Conclusion:
Entering the ranch with exactly enough time to get to the barn and kill aliens is optimal (Case 2).
Entering the ranch early is slower than Case 2 by the amount of time you have to wait until 3:49am (Case 1).
Entering the ranch late is slower than Case 2 by the amount of time it takes to detour for getting timestop (Case 3).
Case 1 is faster than Case 3 when the amount of time you have to wait is less than the amount of time it takes for a timestop detour. On the contrary, Case 3 is faster than Case 1 when the amount of time you have to wait is more than the timestop detour. And of course, Case 2 is always the fastest.