Review: Wenger Synergy rucksack after 5 years of daily use

I am a fan of rucksacks with many pockets. No wonder I like the Wenger Synergy, which has been on the market for over 10 years with only minor modifications. However, I had my fair share of quality issues with this model. Unlike my >40-year-old Swiss knife, this rucksack kept breaking within its warranty period or soon after. It was never a problem exchanging it when it broke within the warranty period, but I got fed up with the exchange hassle after doing it twice. The rucksack's failing part was always the same: the seams of the shoulder straps started to open. I reported the issue directly to the producer, hoping they would change something to improve the shoulder straps. However, when also the third rucksack developed the same problem, I decided not to exchange it but to fix it. My fix is optically not very pleasing, but it has lasted long enough that I can report the second point of failure: the bottom pane. It ripped where the bottom piece contacts the backplane of the rucksack. I also repaired that one because I was interested in which part would fail next. The upside: these repairs were quick and easy, and they have already lasted for 4 months without any sign of failure due to the high-quality material.
 
The zippers limit the ultimate lifetime of perhaps all rucksacks
Now I know: the zippers are starting to have problems. I am surprised that the zippers are still sort of working. The zippers have been the Achilles heel with almost all of my other rucksacks. And unlike a shoulder strap, it takes quite an effort to fix (= exchange) a badly failing zipper. This rucksack is now five years old. I have been using it literally every single day. I cycle or run with it to work, and I do my shopping with it. I travel with it and take it to the summer cottage. Am I expecting too much of a ~100€ rucksack? Is five years' lifetime the maximum I can get out of a rucksack these days? Sustainability is mostly just lip service, whatever the industry. I am determined to keep this rucksack for another 5 years, but exchanging the zippers will cost me at least 2 to 3 hours of work. As a quick fix, I used pliers to tighten the top and bottom wings of the metal slider (like in this youtube video). That has been working, but according to my experience, this tightening needs to be repeated in increasingly shorter intervals, and finally, the metal will break. To avoid replacing the whole zipper, you can add buttons to create a new closure, which is perhaps less work if you are not very skillful at sewing.