How often do yahoo results get shuffled?

Once a month? I think the current results are terrible...

[javahava]

I keep track of results for only a dozen or so keywords related to my industry, but for my industry it seems like the Yahoo results are pretty junk compared to Google (partially, I'm sure this is caused by my own bias because my site ranks well in Google but absent in Yahoo).

I've emailed the Yahoo team and they say I have no penalty, yet a search on my own company name doesn't turn up my home page, but instead my links page or about us page. Seems strange.

I'm hoping for a major algo tweak / reshuffle as the only hope for making these results "right themselves."
Any speculation on the regularity of a Yahoo update?