You can create fixture conditions to make the system try to ensure that all teams play a certain number of games at a certain time or on a certain day etc. 

So for example, if you create a fixture condition on step 6 of the fixture generation process that states "All teams must play fewer than 3 games on any day at 21:00", the system will try to ensure that no team plays more than 2 games at 9pm.

Fixture conditions take precidence over team preferences, and if the system cannot ensure that all teams adhere to the conditions (say because there are not enough playing areas available, or because some conditions prevent others being satisfied) it will warn you of that fact on the suggested fixture list.

You can also add conditions to a league via the "Conditions" button next to the league in the league list.  Adding conditions to the league means you do not have to add them every time you generate fixtures - they remain in place at all times.