Consider the period panties as panty liners. Change the period panties as often as you change your panty liners. Most period panties can absorb up to 20 mL of liquid, so if you often get heavy flow on the first few days of your periods, change the panty after 4-5 hours for better hygiene. If you are wearing a pad or tampon, you don’t need to change the period panty every 4-5 hours; you can change it at the end of the day.