This hasn't seemed to be a problem for Baylor, nor for Oregon State (although I recognize that their posts, while tall, are not as highly rated as those at Baylor).
Since fouls are usually a problem even for elite posts (especially when they are less experienced in the college game), getting minutes for a competent backup should not be an issue. Natalie Butler got plenty of minutes in her "senior" year at UConn despite not being a starter, and those minutes were not generally in garbage time. She played key minutes against both Texas and Baylor.