Pageview API: Limit (and document) size of data you can request
Based on the discussion below, and improved performance, we have decided to limit only the daily granularity endpoints to returning no more than 6 months of data. If more than 6 months is requested, we will return an error to be clear about what's going on (as opposed to the more friendly but confusing truncation of the response).
The main reason for this limit is not performance, or caching, but simply that any API should have some sort of limit. If it's too restrictive, please let us know and we'll consider a higher limit.