Time, when notification is shown is too much. How can I cut it?
There is no built-in way to change this duration.
If you really want to pursue the issue, a community member has been maintaining a PPA with a special version of notify-osd that allows for some customization via GConf. You're on your own if you decide to use it though; there is little to no support provided for software from PPAs.
There is a patched version of Notify-OSD (as ændrük already mentioned) that is maintained in a PPA. To be able modify and configure notify-osd you have to add that PPA and ugprade to it's version.
Then you have to add a second PPA to install a GUI for configuring Notify-OSD
I have been using both these PPA's and can confirm that they work =)