Here is another way to look at it. a big reason why I will never use aspen is because of what you are talking about... It is super absorbent. in fact, it is so absorbent that it is quite possible that a snake can let plenty of fluid out and when the aspen absorbs it, it won't even noticeable. that means that your snake the majority of the time will be sitting in aspen that is filled with poop and pee.
With newspaper on the other hand, I can tell you that even though I have almost 50 different snake tanks / tubs, NONE of them sit on urin or poop more then a day.
A keeper using newspaper (printed or not) or paper towels will on average ALWAYS have cleaner enclosures then those that use other substrates such as aspen.