Hey folks! I've got a 2010 MBP with 500GB hard drive and I think it's about time I backed it up. I've never used Time Machine before and I've had good experience with Western Digital products. I have a few external WD drives already (two 250GBs, one 320GB), so I'm leaning towards another WD one to use with Time Machine. I've read I should get one that's 1.5X to 2X the hard drive size...so 750GB or 1TB? Can you recommend something you're happy using with a similar MBP configuration? Can I plug it in and back up once a week or do I have to plug it in more regularly? Thanks!