I'm not sure I'm asking the question correct, but what I mean is, how long time does TRUE store data on their servers ?

Does anyone know ?

It is driving me insane when I have to test or update websites, sometimes it takes hours before I can see a new update.

Is there anyway to get rid of this or avoid it. It makes it impossible to test your work online.

They keep showing you old data again and again.

clear your browser cache and/or force a reload of the page.

I doubt it's a problem with True cache servers. You sure you have your browser is set to check for new versions of a web page every time you visit the page or set for some some less frequent interval. Like with Microsoft IE you can set the interval...best it's set to check for new versions of the page every time you go to the page. See image below. And the browser cache clearing/refresh many times helps also.

It is a problem with True and their "traffic shaping".

I know about F5, clearing cache etc.

I experienced this problem a while ago.. and ctrl-F5 does nothing.

It lasted for 4 days then new content was displayed.

For testing purposes, you could use a proxy or TOR, either of which would give you the current version of the website.