I'm in 2016 in my Man united saved game and I came across this thread, and I realised that I've actually sold most of this team and replaced them lol. Only players I've kept are Fabio, Rafael, Vidic, Evans, Evra, Carrick, and Hernandez. I've done pretty well so far, won the PL 3 out of 5 seasons, FA cup once and CL once (for some reason, I can't win a cup + league in one season yet... so I'm working on that). This is pretty similar to how I started the game. I made no expensive signings, and only bought wonderkids/hot prospect youths to cover the positions where age is becoming an issue, and developing the CM. Man United squad will keep you at least challenging for the league without changing it for a good 2-3 seasons. But at that point players really do need replacing. I personally think for at least the first 2 seasons you should focus on buying youths, as i mentioned, for the key players which are closest to retiring and becoming old. EG Ferdinand, Scholes, Giggs etc etc. This means that by the start of the second season if you've done well you can buy a world class GK such as Akinfeev who won't need replacing in years, and by the 3rd/4th seasons you will be able to sell the youths who haven't developed as well as you'd have liked and some average squad players and bring in some real top class players.