Construction is key when it comes to the longevity and durability of a sofa. Sofas constructed of hardwoods (such as walnut) will outlast those made of softer woods such as pine. Not sure? Ask the sofa manufacturer about construction materials.
Another important ask relates to sofa springs. Metal coils often break. An eight-way hand-tied sofa spring system is preferable, and a signature of a well-made, crafted sofa. Expect to pay a bit more, but it will be worth it in the long run to have a sofa that is built to last.