Yes you can wash your mattress protector.
Mattress protectors are meant to be washed and to keep your mattress protected.
Wash your mattress protector with a mild detergent (with no builders) and avoid adding bleach or chlorine to the washing machine.
After the protector is washed, complete a rinse cycle to ensure all the detergent is out.
Any leftover detergent can cause mold and mildew to develop.
Bed Sheets should be washed at least once per week.
I change my sheets on my bed at least once per week.
I always have fresh clean washed sheets available and then usually Friday night or Saturday morning I will remove my old sheets and replace them with fresh new clean sheets.
Then I wash the old sheets and put them back in a closet where I keep sheets and other bedding.
Most people should wash their sheets once per week.
If you don't sleep on your mattress every day, you may be able to stretch this to once every two weeks or so.
Some people should wash their sheets even more often than once a week.
According to a 1,000-person survey conducted by bedding reviewer, Mattress Advisor, the majority of people change their sheets every 24.4 days.
When you do the math, that's about three weeks and three days of sleeping in the same sheets.
As to how often you should replace your bed sheets?
It's recommended that you change your bed sheets every 3 years or so or when they get worn out or look torn etc.