And to add to my previous post, Ib...
You need to play bench players in order to;
A) keep your starters minutes in the 50-80 minutes per game range in order to IMPROVE your gameshape upon the end of the week.
B) increase stamina, decrease tiredness. during the minutes which your bench players are on the court, their stamina will be better then the starters at that time, and could give you different match-ups, and rest your starters so they have better stamina during the final portion of close games, then end of quarters, etc.
C) to train some players. All your players are old farts, pick up some young guys to play some back-up/scrimmage minutes for some training so your team continually improves throughout the season.