The insert that comes with the fuzzis is made from microfibre... To be honest I think 3/4 hours from that isn't too bad, I know I have to change Isabelle that often anyway or her skin gets sore!
Fleece itsself isn't absorbant.
Hurray to no leaks overnight though!!
And yes - putting the fuzzi insert over a home-made (or bought) hemp booster/insert sounds like an idea combo!!