What makes a backpack last longer?

Just don't throw it everywhere, or wet it too much or anything... take care of the zippers, and don't put it near flammable or sharp objects. It also helps if the quality of the material of the backpack is good! I use jansport. It's high quality and it lasts long with no effort from me at all.

I don't think backpacks break that easily. I've had a backpack that lasted 5 years. I guess the brand might be important so it's alright to spend a lot of money on an more expensive backpack because they last a long time.

I think the most important features of a backpack are the fabric it's made of and the quality of the stitchings.

The quality. When my kids were young, they always wanted the plastic bookbags with cartoon characters on them and they would last a half of a school year if I was lucky. Now I only buy the strong ones made of canvas with a good thick zipper. I think the more books that the kids carry and the heavier it is, the quicker it starts to bread down. I used to have them hang them on a hook on the wall, also and have found that doing that only wears the handle down, so I have them set them on the floor.

check first the required load limit and the load limit you need when buying this stuff, second the material used, for durability it must be made of canvas, nylon (polyester), either ripstop fabric for lighweight packs or havier fabrics such as condura for more typical usage

The quality of the material is made from. The quality of the zip in the backpack. The other thing to see while buying a backpack is to see whether it is water repellent. Am not talking about some raincoat or jerkin, a backpack. Whenever you get drenched in rain, the material or the leather in the backpack gets torn out, due to excess usage after it got drenched. So check whether there is a separate layer of water-repellent, and ask the person who sells you the backpack, what does it has to do with water-resistance or water-repellent?