From my experience stamina also plays a role in the chances of getting 48 mins. I've thrown out a lineup meant for 48 mins and had an 18-year-old with atrocious stamina always get subbed out at 45-47 mins. Could be a coincidence or could be accurate.
2x NBBA Champion: S55, S56. 3x USA Cup Champion: S54, S55, S56. WR for longest home streak ever at 11 in Season 47.