Just how does Play History work?

Sometimes i can find the events i'm looking for on it - and sometimes can't. Sometimes i've got nearly 30 pages of history, sometimes just 3 (i'm assuming a cookie or something was deleted?). Some pages are screens and screens and screens long, others barely need the scroll bar moved to see everyhting on the page.

What determines a new page? Where is this info recorded? (if on the server, then why doesn't it go back a unifrom 30 days or something?) What is it i'm doing (if anything) that gets rid of pages?

Interesting. So it should give 14 days of history - but if i'm checking it right after a reset (or something) maybe it's only got around to downloading 5 pages of it? Don't know if it was right after a reload when i was checking it before writing, but it was then only showing about 5 pages of stuff going back two or three days (which is why i couldn't find what i was looking for), whereas checking it just now - it goes back the full 14 days (for 117 pages)!

Good to know that one just needs to give it a bit of time if it's not all there yet.