There seems to be issues with how long the Balloon tip takes to vanish even if you set a low duration (as show to be 3 seconds in the code below).

notifyIconMain.ShowBalloonTip(3000, "XYZ...", MyVar, ToolTipIcon.Info);

For more information see my blog post on this subject: http://blog.lyalin.com/2007/12/showballoontip-problem-in-notifyicon.html

Since Microsoft have neglected to provide this essential information, I'll do it for them. Ensure HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\EnableBalloonTips is set to 1 if your balloon tips don't show up at all.

I believe that the timoutvalue is given in seconds, It would be nice if Microsoft could verify this small piece of information. Also I have read something about a minimum time of 10 seconds, my own tests points to that this is true but I get some inconsistant behavour.

The default nimum and maximum timeout values are enforced by the operating system and are typically 10 and 30 seconds - i.e you cannot go below 10 or above 30. However, I swear that lot of time it displayed more than 10 sec even the setting was 10.