I have used up several backpacks. All were of the UL variety. You really aught to become a full member to read the recent articles on the site. Even the older ones still have good stuff in them. Knowledge makes a good camping companion.
Light weight, Ultra-light(UL) and SUL packs are all I use for the past 15-20 years.
I started with an old Kelty external frame, moved the next year to a lighter internal framed Tough Traveler dropping over 2 pounds. I still have both after 35-40 years of hiking. Before, that I had a variety of old military packs. I have one left, the lightest of the lot, that weighs about 4-3/4 pounds. These were rugged, durable and required next to no maintenence. All were on the 2-5 pound category.
Around 1970 or so, I *did* go through the Tough Traveler reinforcing seams, cutting away at the hems and burning the frays with a lighter. I found that all packs can use some pre-trail preperation. As the mnemonic goes, "A stitch in time saves nine." I don't wait for something to fail...reinforce it before heading out.
* Double stitch press points by about 1/8" seperation. Shoulder straps, hip belt mounts, pockets, straps. Do not go over the same stitch twice!
* Burn/seal all frays. Frayed threads, fabric edges, strap edges...
* Add some narrow strap to hip, shoulder straps. The Gossamer Gear packs I use do not have a strap over the shoulder, for example. Bottoms get a couple lengths where it helps to reinforce it.
* If needed, add four or eight small attacment loops: Reinforce with a small piece of fabric (about 1-1/2" square) and melt small holes for short 2mm-cord loops.You can seal these with a dab of silicone calk.
No, I am not a good taylor, I just redo existing stuff. Reinforcment stitches can mean a couple years of extra life out of a pack, though.
Most packs can use a bit of seam sealing. I dilute silicone calk about 10:1 with mineral spirits and do the whole pack...inside and out. This locks in any fibers in the cloth with the others, locks in stitching, and supplies water resistance to the pack. between the extra stitching and seam sealing, it adds about an ounce of weight to the pack. So, removing any un-needed loops, rings, excess strap and mounts helps to keep the pack about the same weight.
Generally, you will find that I don't worry about gear on my outing. It works or it doesn't. I lost a G5 when I broke a piece of rock off comming down a peak. I slid down about 10-15 feet and really ripped the bottom and both pockets. I simply rearranged, added a bit of duct tape to complete the trip and retired it when I returned. This stuff happens to all of us, sooner or later, if you go out enough.
Damage is repaired when I return. The Miniposa lost the center strap keeper a couple times. The fabric "frayed" where I put my stove. And, I put a couple small holes in the bottom over the years. I do not wait for these to get worse. I repair them before I take the pack out again. Generally I clean the pack, apply a sticky patch (cut down as needed) and stitch around them, including an "X" across the hole. I mention the Miniposa, because there are patches on the patches around the bottom. This is part of the maintenence of all packs. All packs require maintenence. Patches, stitching up a loose strap, replacing buckles or loops are all part of good maintenece.
Even with good durability and maintainence, I still have lost packs. This leads to reliability. A good reliable pack will *always* get you home. Even if you have to do a field repair, it will still work. Some things are not repairable. Plastic frame sheets, for example. They can crack and break. I have found a couple sticks work well in place of them. When I got back, I replaced it with a couple arrow shafts. A hole in the fabric is easy, just cover it with duct tape, sometimes both sides.
But, I never think of protecting the pack. I think of the pack as a protection for my other gear. Durability can be enhanced by pre-maintainence. Perform maintence as soon as is possible. You *will* get good reliability out of your pack.