Originally oldies had relatively high wages to make them money-eaters and force teams to developing, there was also age limit 31 or 32, when player's market value dropped to 0 and you couldn't sell him any more. At some moment banks were introduced as players in that age were useable, there were couple of star value and price reforms too.
With my first team I hoped that my ST mid (was #2 mid in Estonian NT after legendary Kuusk) will carry team over non-buying period to save money for stadium, but he still aged too quickly and I had no adequate successor to replace him. Team of oldies will never bring any profit from market as their MV only drops. Both my teams have based on youth development and promoting/selling. I very rarely buy some "ready" player because of high price and usually they haven't been worth it, they didn't make expected change. My last bad experience was with my first team, when in relegation danger I bought on midseason window 2 mids who seemed to be ok, but they couldn't bring me single additional point comparing to first half, with them I got same points as without them and -25M after selling them. Ofcourse they couldn't save me from relegation too. Now team is back in L1, but clearly too early and will go down again probably with some negative records for club.
I suspect that I have to make some refresh after this season- several players are 26-27 and can't develop further, but losing their value. Meanwhile I have some bad youth seasons and some more promising players are 16 at the moment. So my big hoped comeback will wait probably some 10 more seasons.