Duration of Alerts
A modal alert has a duration of FOREVER. A timed alert, by default, uses the default duration of the device.
Choose default durations for timed alerts that are long enough to allow the user to read a screen full of text, but short enough not to frustrate the user's progress through the application. Because timed alerts have little text it is reasonable to expect users to need one-half to two seconds to read them. The actual default is best determined through usability testing on the device.
Use the MIDP implementor's default duration for timed alerts. An application is more portable if a timed alert's duration is device-specific, not application-specific.