If you want to buy a settee that's going to last a long time then the truth is you really do get what you pay for.
A well built quality sofa will last a very long time.
Consider the covering as well, as the harder wearing this is and the more stain resistant the longer the fabric will retain it's new look.
When choosing your fabric ask the supplier about a rub test value.
Good settee fabrics are tested for the amount of rubs it takes before the fibres begin to show signs of wear.
A quality fabric will endure at least 30,000 to 40,000 rubs before deteriorating.
However it's not always about longevity.
The settee you bought 10 years ago, however fashionable at the time may now appear dated and clash with the new decor in your house.
Rather than replace it, consider having it recovered to suit your new decor.
This can be expensive but if your settee has stood the test of time and it's only the aesthetic you're worried about then it may well be cheaper than buying a new one.
Another route to take is to purchase a modular settee or sofa system.
There are several suppliers that have designs that you can individually replace each component from stock and cheaply.
This means that new covers can be purchased off the shelf without expensive upholstery costs, new seat foam can be bought and should anything have happened to frame components, these can be replaced to make your settee good as new.
If you purchase a modular system you then have the option to add more units to you 2 seater settee, even turn it into a corner settee.