Since you haven't used it yet, no idea if it as great as you think it is by my definition. I thought Osprey packs would be great for me, I can't wear the lighter packs of that brand at all because even a light load in an Osprey makes my back hurt.

I'd pack it and go for dayhikes for a while. See how it works out. If you weren't measured for size it may be inaccurately sized, that shows up fairly quickly in discomfort or just not being able to get the weight where you want it (on the hips, mostly).

I use a 40 liter pack for many of my 3 season trips, and depending on what I need to take for food storage could probably do a week with it. What will change for longer trips is the amount of food you take and if you need a bear canister, the size of the canister. If your gear is minimal you'll easily find there's space in the pack for all but the largest bear canister.