@Dre: I dont necessarily recommend a deload week at any given interval. I PERSONALLY take one every 8-10 weeks but thats because the program I follow has that built in as part of the progression.
I know of guys who train their asses off 10-11 times a week that almost never deload (See: Chaos and Pain blogspot). We're talking 10-15 sets of 2-3 reps on big exercises, with weights in the 300-500 pound range.
I think the larger issue here is that people feel tired on Thursday and Friday, their arms are sore, and start thinking they are over trained, when in reality it takes a phenomenal effort to get over trained.
Dr. Lonnie Lowery often quotes a study where, in order to get people to an over trained state, they had them bench their 1RM 10 times a day for 2 weeks straight (or something close to that) - So the fact that you have a back day and an arms day throughout the week doesn't lead to over training. 10 max effort attempts a day for 2 weeks straight, THAT'S the kind of effort we are talking about.
Here's the deal - If you are BUSTING YOUR ASS in the gym 5 days a week, chances are you ARE NOT going to feel great every day. I personally live with some amount of soreness, somewhere on my body, every day of my life. It is honestly painful in my legs to sit down on a chair 3-4 days out of the week.
Get this, some days I feel pretty damn tired too. That's just how it goes when you ask your body to put forth a huge amount of effort, sometimes twice a day, 5-6 days of the week.