From MozillaZine Knowledge Base
This preference determines the amount of time between checks to see if an update-related timer should fire.
This preference is now obsolete; it has been replaced by app.update.interval, measured in seconds.
Possible values and their effects
The number of milliseconds between checks to update-related timers. (Default: 600,000, or 10 minutes)
First checked in
Has an effect in
- Firefox (all versions before 1.0)
- Thunderbird (all versions before 1.0)
- Mozilla Suite (versions?)