I use news paper and dcl cage liner. first I put down a layer of news paper, then the dcl cage liner over that. This is how I have kept every ball python that I have from day one. When a female is gravid is the only time I will put some moss or mulch in for nesting. Snakes will lay their eggs on just paper though. When using paper there is no spot cleaning, when they deficate all the paper is removed and the enclosure is cleaned. This is more time consuming, but a far healthier enviroment. Spot cleaning does not get everything left in the mulch or aspen and in my opinion the enclosure is still dirty. The best thing is there are no bugs in the news paper. Mulch is the perfect place to breed mites and that's about it as far as I'm concerned. I have close to 200 hundred snakes (more with babies) all on paper and all doing great.
Jon