Wish I knew about these when I first got my period, it makes that time of the month not so dreadful! These work wonders, even with a heavy flow.. It literally is so comfortable and you completely forget that you have your period, you feel like you can conquer anything, even with the PMS! So easy and hygienic to apply with the applicator, anyone can use it! Id say they need to be changed at least every 5 hours, and just to be safe, still wear a panty liner, just in case it leaks on the first few days..