Hey Chris, I stained the insides and sealed with several coats of water based polyurethane. I sprayed the pieces prior to assembly to ensure all the corners were well covered. After assembly, used kitchen/bathroom caulk on all seams.
The cage has been fully populated for over 10 years. I do have some staining from urates/feces on the lower portions of the wall. Does not appear to have really affected the integrity of the finish. For my second cage similar to the first I went with formica on the sides and ceiling as well. I don't like the staining and I figured this would be bulletproof.
Another trick I've picked up lately and somewhat by accident. My sections are slightly smaller than standard newspaper. When I started using newspaper instead of indoor/outdoor felt carpet I found I had to press the paper into the corners leaving a half inch going up the sides and back. Well as I'm sure you've already anticipated, this limits the contact of solid urates and/or feces with the wall. WOOHOO!!! What does not get stuck/smeared on the wall, does not have to be cleaned off of the wall. Since then I have switched over to dimpled craft paper and I cut my pieces even larger that newspaper, now I have 1.5" - 2" riding up on the sides. Even better protection, plus makes kind of a bowl which holds the urates even more. BRB's pass liquid urates often and in volume.
So now for cleaning cages it's put the snake in a container, remove/clean the hides and water bowl. Fold up the paper liners, I usually have two layers of newspaper under the dimpled craft paper to help soak up the urates. Spray down and clean the floor/sides/whatever necessary. Re-paper the floor, replace the hide/water bowl, return the snake.
-----
Thanks,
Dave "Rainbows-R-Us"

0.1 Wife (WC)
0.2 kids (CBB)
4.12 Brazilian Rainbow Boa
2.1 Hypomelanistic BRB
0.1 Het for Hypomelanistic BRB
0.1 BCI "Elvira" normal from 1989
1.0 BCI albino / het-anery
0.1 BCI Hypo / het-albino
0.1 BCI Anery / het-albino
0.1 BCI Hypo (possible super)
1.0 BCI albino het stripe
1.0 BCI salmon hypo
0.1 BCI ghost
lots.lots.lots feeder mice and rats 