Is there a need for me to record color bars onto each minidv tape if they're all being recorded on the same camera? Under what circumstances would I need this, other than after doing my final export from my NLE?

I like to put them for 30 seconds at the front of the tape before I record any material, just as a buffer; I also use them if I have different scenes or separate days on one tape, it helps keep them separate.

The section of color bars also helps protect the real footage from damage by ensuring that it isn't at the very start of the tape (a common problem with all video tape formats).

1- Sometimes you can spot problems with camera settings through the color bars. Controls that affect digital levels will usually affect the color bars too (though not always).

2- They can be helpful when editing, since it's difficult to grab material from the very first few seconds of a tape.

3- It might be helpful to record some room tone/ambience onto the very beginning of the tape.

4- You don't really need to record color bars onto the beginning of a tape. But it can generally be helpful.

Here's why we put color bars on tape.

1. 90% of tape dropouts occur in the first and last minute of a tape (more stress and tape threading abuse at these points).
2. Even though most people are non linear bars provide a reference to calibrate your monitor, edit system, audio mixer (assuming you put a 1Khz tone with the bars) and provide a reference for QC.
3. If you need the first second/frame of the first shot on your tape you already have 30 sec. of bars to provide a preroll for your edit system.
4. You can verify that your camera is working properly before your run and gun producer shoves you into the fray.

There is no good reason not to put bars on your tape given the above.

I make it my religion to put 30 seconds of bars at the head of any shoot tapes, as well as master tapes. I tend to also stick at least 10 seconds of either bars or black at the tail of my shoot tapes (unless I am scrambling to get a new tape in and can't spare the 10 seconds. Also, master tapes always get at least 30 seconds of black at the tail). All for the same reasons given above. It's one of those small disciplines that will eventually save your butt sometime down the road when you least expect it.