Our month-long search is restricted to only coach class at the moment.
When we've experimented with a month-long search in higher cabins, we've found the results very confusing, since in many markets it's not possible to be in first class the whole way between the origin and destination. And it can be further confused when the cabins available depend on the day of the week. This can lead to a situation where the prices on different days wind up being apples-to-oranges comparisons.
We're still playing around with some ideas, and hopefully we'll add that feature someday.