Changing Default Tooltip Delay for all Applications

The TooltipService.InitialShowDelay allows you to set the amount of time that passes between when you first hover over a control and when a tooltip pops up.  This value defaults to 400 ms (0.4 secs).  This default value actually comes from a registry setting--MouseHoverTime--that dictates this delay for all applications.

You can find the MouseHoverTime registry setting at: HKEY_CURRENT_USER\Control Panel\Mouse

You can change this registry setting by entering a new value for the delay (in milliseconds).  You'll need to log out and back in before the setting will take effect.

If you change this setting, applications that do not explicitly specify a value for InitialShowDelay will pick up the new value from the registry.  Applications that explicitly set a value for InitialShowDelay will still use their explicit value.