I just started this game and is this usual?

Q u o t e:
Hello all, I just started WoW about two weeks ago, last week the maintenance was extended by far.
Today..The servers are still not up and I'm not hoping for another extended maintenance.
Is it usual that Blizzard does not follow there ETA, or is just bad coincidence for me?

It varies actually. Over the long haul, maintenance periods are typically completed on time or prior to the estimates provided. Sometimes issues arise which require further attention, and so the realms remain unavailable until those issues are resolved. Alas, it is far easier to notice those times when maintenance is extended.

Please keep in mind that these maintenance periods are necessary, and that the times in question are estimates for a reason; to account for the possibility that further work may be necessary.