I’d like the cube to be at LocX = 5 at +0.43 seconds. Which frame is it? At #10: No, this would make the cube too fast. At #11: No, this would make the cube too slow. Based on a time scale this wasn’t a problem. You are trying to change the physics of objects. This is not valid.
And what if you like the cube to be at 0.441 seconds? There is no frame asociated with that. It is just a smooth interpolation the computer does for you. At 24 fps, the duration of one frame is 1/24 seconds. Why, in your case , would you want to be able to place different keys in that 1/24 seconds, if it to be perceived as a simulatneos action anyway? And what if you fall in between frames?
Why would you like variable framerates??? Psychologicaly, the eye percieves movement at 24 fps. In that framework, the human mind recognises an action if it is within 5 frames (not my finding, just the teachings of a well known animator). So why waist effort at higher framerates?
You could put a cube at frame 1 at posistion 1 and in frame 647 at position 2. The computer interpolates it for you. That is the work that tweeners used to do. If it goes to slow, just use the time ipo or remap it, move the jeys/ actions closer together or whatever.
Maybe for live action movies, they use time as an indicator. But in animation it is all about frames. It is not a limitaton of the software, it’s a limitation of the fact that media (tv, dvd, video games, film) is a succesion of still frames. There is no continous time. Only the fact that the human mind is fooled that time is continious at 24 fps.
Why do we need higher refresh rates for television (like the brilliant 100Hz tv’s, or high refresh rates for monitors)? That is because in between frames, the phosphor colour elements fade a little. That is the faint flickering that makes you or your eye tired after watching tv for a couple of hours. At higher refresh rates (No, framerates stays the same), the phosphorous elements fades a lot less, making it more pleasurable to watch tv.
Now for the games frame rates:
Normaly for games to appear fluent, you need a complete new image between vertical blanks (that when the electron beams goes back up to write the next image). 60 or 80 fps for games is just a quality indicator. That means that for a monitor refresh rate that is lower than the maximum fps, a new image is garanteed in between vertical blanks (=vbl).
If the fps is lower that the refresh rate or out of sync (in case that no interrupt is used to time the image construction), the action still could be smooth (provided the fps>24) but tearing could be visible. Certainly for game console, high fps values is pure nonsense. You want to match the TV refresh rate (25 fps or 29.7 fps) to keep things running smoothly (note: not completly true… but for 99% true).
But the main message/ conclusion is: Our current state of visual technology is all based on descreet images. The perception of continous time is just human perception. And if you want to work based on that illusion, you in danger of basing your timing on non existing frames or messing up current frames. It’s not the ‘old and outdated’ way of doing things… it’s the CORRECT way of doing things.