These are great to sleep on.  They do very well after many Washing/Drying.  But these even make chores a lot easier!  It takes me forever to get my cotton cases on pillows. Not wrong size but still purchased larger ones but just a waste or $$.  Now I put the satin case on & then put cotton one on, WOW what a difference!  Took about 3 seconds.  Pillow slides right in, no tugging, no sore arms.  My cotton cases have a zipper at one end so no worries of slipping & sliding.  Thinking about sewing open end of satin cases closed while on pillow.  I think would be nothing wrong with that.  Pillows have covering on them of some sort when you buy them anyway.   Would cut out a little more work doing household chores.  I'm all for that.  Regardless of how or why you use them, they're well worth the $$.  I highly recommend.
Kali