If you buy a backpack from any reputable mountaineering store, you should get a very good item. For example, I had a North Face backpack for many years. It never wore out, and the seams remained strong. You will pay more for a genuine mountaineering backpack ... but that's because the users expect these items to be strong.

One important thing. Normal backpacks are 'external frame packs' ... meaning that the frame is on the outside of the pack. Mountain climbers generally use internal frame packs. So you need to decide which type you want.

I agree that it is very handy to have a lot of pockets. the biggest problem i had with my old North Face pack is that it wS necessary to dive through all the contents to find some small object ... usually at the bottom of the pack.

I am sure that there are a lot of cheap junky backpacks in the market. My advice is ... dont buy at those stores. go to a reputable outdoors store and try their products.

BTW, I agree with earlier advice. REI is an excellent place to buy a pack. And you should take the time to learn how the pack works, and how it is intended to fit your body. Time spent choosing good gear ... is always time well spent!

About your final question ... The backpacks that you buy at REI will be fine for a 1-week hike. But it all depends on how much gear you try to jam in your pack. There is NO SUBSTITUTE for experience and good judgment. And that experience only comes from doing a lot of trails. So start simple - and build up. Have fun!!

Good luck.

Pete