I want to select a KDE distribution, My measures are :

- good support in bug fix and update (it is most important for me)
- long time support (about 2 or 3 years)
- i prefer debian based distributions
- large community

thanks.

I'd say Kubuntu meets all your criteria (the currens version has long time support), I have the current Kubuntu istalled on my laptop and I'm very happy with it.

Alternatively, you might consider Mepis. I don know if they have promised long time support, but generally their release cycle is much less hectic than most. Mepis has a good reputation wrt. difficult hardware.