One thing I think separates the Humble Bundle from the Indie Royal bundle is that Humble Bundle games always work on Windows, Mac, and Linux. I primarily use OS X and Linux these days, so that's a big incentive for me, and helps keep my "fatigue" down.

That said, if this turns into a never ending string, the amount I contribute towards each bundle would likely drop since frequency would be going up.

Probably something for the Humble folks to investigate - which performs better - more frequent small bundles or less frequent larger bundles.