I can compile a 20-slide file (no tikz) in less than a second.
Of course, larger slide decks will take longer and I'm sure tikz
requires considerable CPU time, but what do you mean by "huge"?
Also how big a slide deck are you talking about and what percentage
of the slides use tikz?
About 1500 slides (350 actual frames with overlays) for a 20 hours course.
LuaTeX + opentype fonts makes it even slower. Some complex slides with
animate algorithms (mergesort, ford fulkerson, stuff like that)
Ok, I can split it in lectures (albeit that's not so simple to use \lectureonly without
breaking toc). I can use the externalize library. Etc.
Anyway, what's bother me on the long run is that it is only slides. The browser is able
to render / typeset the text and graphics by itself. No need to resort to such complex
compilation (there is MathJax, and stuff like Raphael.js and jQuery that could do the job).
The more powerful your tool is (luatex, opentype fonts etc) the more you lose
time with details.
PS. It's all idle curiosity on my part.