bath towels: weekly
bedding: every 2 or 3 weeks, depending on the season
Reverse this for me. I shower first thing in the morning every day and my bath towels are just drying clean skin. They only touch me for maybe a minute or two before being hung to dry.
However, I go to sleep at night, after a full day of developing natural body oils on my skin. And I lie in bed for 8+ hours at a time.
My bed sheets are far more gross after a week of use than my towel will get in a month, more or less a couple weeks.