Time Machine Question

I've never used it before, just cleared my old external HD and set my macbook up to time machine.

It's been going for 4 hours now and is almost done.

My question is, when I back it up again in like a month or so.. if not much has changed on my computer, will it only take a few minutes the next backup?

And, can you stop a backup at 90% or something, eject the HD and resume it at another time?

 

Thanks for the answers.

One more question about time machine and more directly garageband in association to time machine.


I went to the genius bar and asked them and they didn't even know. What I asked was; Where are custom made instruments saved on the computer?

For example. If I take an old song into garageband, break it up, sample it, and assign it to keys so It can be played on a MIDI keyboard as an instrument.

These "Custom" instruments are saved into garageband itself, NOT individually saved garageband projects.

So when opened on another computer, these instruments do not work.

So my question is how do I save them? Where are they saved on the computer? And will time machine restore them all in event of an HD meltdown.