Balenciagas are very light and gorgeous...however I really am unsure whether they would make a great everyday bag for over five years. I know many might disagree, but their handles darker, the leather can be delicate (on the newer ones), the tassles will split or break...I love them to death, but can't imagine how one would hold up w/ everyday use for many years.
I agree that an LV is a forever bag, as long as you get the monogramed canvas. Guccis also seem to hold up well. You can really tell because so many people still have their vintage LV's and Guccis, have used them everyday for over ten years, and they still hold up well. LV even has a good repair program to replace straps and the interior of bags, so even if you do manage to destroy one after 5 yrs, you can repair it instead of replacing it!
Good luck! LV would definitely be my recommendation (although I loove Koobas too an feel they are very underrated- haven'[t had mine that long yet though to tell you how they hold up).