The life expectancy of a modern computer is about 5 years. Anything over that is a bonus.
My advice, buy another one. I wouldn't bother building as, apart from the fun of doing it, it will certainly not save you money. MESH computers sell on what they call an open-case basis. In other words opening your case to add or upgrade hardware will not invalidate your warranty. You could also check with other manufacturers suppliers to see what they say about this.