By trips, do you mean hiking trips (trekking)? Or do you mean "backpacking" in the "traveling across Europe and staying in hostels" sense?

I ask that because the pack you link to appears to be intended for the second group.

For hiking/trekking, a 45 liter pack may be large enough, but it depends entirely on one's other gear. Most beginning hikers take traditional gear and too much of it, in which case a 45L pack usually isn't big enough. On the other hand, an experienced lightweight or ultralight hiker can easily fit all their gear and a week of food inside a 45L pack.

Another issue is that the EC pack you mentioned weighs 4 pounds 9 ounces, which is a lot for a 45L pack. For lightweight hiking, it's easy enough to get a good pack in that size range for 2-3 pounds total weight. (The real ultralight hikers are using frameless rucksacks that weigh 8 or 9 *ounces*, and their total pack weight is about what that EC Pack weighs *empty*.) The REI Flash 45 is about the same price as the EC pack, and weighs half as much.

If you want to go hiking/trekking, then I would urge you to go to a backpacking/hiking specialty store and see different kinds of packs. Get fitted, and try them on with various weights of gear. It's usually best to buy your pack last -- once you know what other gear you have -- so it all fits.

Hope this helps.