Time Machine question

I have a 13" MacBook with a 120GB hard drive. How long should Time Machine run to do a backup? Mine has been running for over 2 hours! TIA.

???
How much data are you backing up?
Are you doing it wirelessly, via ethernet, USB, Firewire?

First backup - let it run overnight - yes overnight.

Time Machine

I've done about 30 backups with it. I had a hard drive crash; they replaced the hard drive with a brand new clean one. Today I restored the whole drive in 25 minutes. To be safe, I started a backup of today's system and it's been running now for 2.5 hours! It's already at 14.7GB. How did it totally restore itself in 25 minutes but is taking this long to do a backup? It's never taken this long before.

Time Machine

I'm using a 250 external drive with USB cable.

Scratch that post.