I wash all my fleece linings by hand with detergent, rinse off, then soak them in vinegar water to kill the bacteria.
Mine use their hay pan as their bathrooms so the fleece portion don't get much pee, and I know this because I can see there is very little urine in their fleece liners and fleece pee pads. I wash the fleece pee pads every three days, and change and wash fleece liners every week.
Their hay pan or their "bathroom" get emptied every other day, and filled with hay over again. I put puppy pee pads on the bottom of the hay pan to collect pee so when they eat hay, it is not entirely soaked in their pee. I also top off hay often throughout the day. Mine are indoor piggies so I check on them routinely.