Buying a new boat does not mean it is ready for deep water, sailing or cruising! When purchasing a boat, have a clear plan of its use! For example: A ski boat would be differently configured than a fishing boat. Manufacturers are under the pressure to build a good looking, cost effective boat. If it is too specialised the market for the boat is smaller and more difficult to sell! What it means expect to spend more money outfitting a new boat, a used boat may already have all the gear needed!
The boat is too old, need a new one! Fiber glass hulls if well built do not deteriorate. The wood, aluminum, steel all eventually do! Yes! it can become too old then! Buying a new boat is market driven, if the boat is too good you will not buy another boat. Therefore, a manufacturer does not want to build you the best boat, but just good enough! Another way of explaining it is! Build a product too good, the person who bought the product will never come back because its not needed, but if customer buys a product just good enough and happy with it. When it needs replacing he will come back. Now one can make a lot more money!
A boat is expensive! It depends, a large party boat yes! A small rowboat with a small engine no! Know your budget! Engine maintenance costs money! The boat with two engines cost twice as much to maintain. Sails do not last forever, the caulking on the boat sometimes needs to be redone. Cast iron exhaust manifolds, on inboard water-cooled engines need replacing every 5 to 8 years in saltwater conditions. A maintenance schedule is very important!