Splitting Workouts (Morning/Night, etc.)

Say you had a killer squat session and really felt the burn, but had no time for leg extensions that were on the schedule. So you down the protein and go to work, etc. Would there be more benefit from doing a hard series of leg extensions 4 hours later at lunch (or 9 hours later after work, etc.). Or is this just tearing down the important “first few hours” gains from the earlier session?

The leg extensions aren’t necessary. You got some hard squatting in.
Unless you were just using them as an example, i wouldn’t say its all that important, just fit them in next time you got the bulk of your workout done.

Yes if you have time later to finish your training, it’s a good idea. In theory it’s even better to split your workouts up in segments over the day rather than all in one workout. I personnally never noticed the difference but then again I never did that regularly, just when in a pinch. I do notice a drop in strength if I don’t get a full session in though.