Take your Stock line chart example: how would you greatly reduce the number of labels on the X (time) axis?

You have approx seven months worth of data, and the number of labels is excessive. I have a stock line chart based on your example, but with >2 years worth of data, with a data point available on virtually every weekday. The number of labels that gets rendered is massive, and the X axis is unreadable.

How to reduce the number of labels to have a label + dash every (say) three months?

Looking at the source, it would seem that the real problem is one of reducing the number of "inflections" on the X axis, since both the rendering of labels and grid lines is keyed off the number of inflections. (A per-label inflection is only hidden if it would intersect with the previous label; i.e. you're trying to render as many as you possibly can, which I don't think is a good idea - unless the behaviour is overridable.)

Any help / guidance would be welcome.