The liners are made like a layer of fleece, layer of cotton batting, layer of towel although some people make them with fleece-towel-fleece, fleece-batting-fleece, etc.
I don't have liners, I just use plain old fleece material or fleece blankets cut to cage size spread over newspaper and puppy pads.
Auzzie-I spot clean the fleece at least once a day, twice if I am home all day. When I get ready to change it out and put fresh fleece down, I roll it up with all the poop inside it, bring the side ends up together and take it outside in the back yard and shake the poop off and then throw it in the piggie basket to get washed. If you can do laundry every week you will need 2-3 changes of fleece. I have 5 changes right now but I only go to the laundromat every 2 weeks.
My piggies love it and fleece is all I have ever used with my girls. CoCo hardly ever sleeps in a hidey box or cozy, she loves her pillows and sleeps on those usually with her head or upper body on the pillow and the rest of her stretched out on the fleece. I don't feel I am a slave to the poop because at the most it takes me 5-10 minutes with a small broom and dustpan to spot clean each day. You can get the small broom/dustpans at the dollar store.