There is no magical number as to how many years a suit can last. It will depend on the fabric and construction of the suit. For example a custom tailored wool/cashmere suit will last a lot longer than a polyester bargain brand suit.
Most often you get what you pay for. If you are looking to buy a suit, buy the best suit you can afford. Choose great quality fabric, a wool suit is one of the most durable. And don’t choose a very trendy style as this will date and you will not feel comfortable wearing it after one season
The price of a suit goes much more to the quality fabric than how it will look. Meaning, a more expensive suit won’t automatically look better than a cheap suit, but a cheap suit will very likely not last as well/ as long as a more expensive one.
Own at least a black suit and a gray suit; buy a navy blue or other shade of gray suit after that. Blue and white shirts can’t go wrong.
Tailor tailor tailor. It’s a marginally inexpensive investment that pays off – for example, it will turn that cheap suit into a sharp looking suit. See below.