To my understanding from your POST ,
You are having checkpoint at every log switch ( ONLY ), and log switch is occuring ( 15-18 time )when the redo log is getting filled up. That means you have a big redo size , that will be absolutely OK. Only disadvantage here is your recovery time will be more.

In my DB(s) , i have manged to have 24-30 checkpoints/log switches a day.