If you were using the watch for a night dive you would want more than 30 minutes of legibility. The night dives I've done we used our diving lights to charge the watches and gauges before the dive, so 12 hours in bright light should be more than enough.
If you have a need for the lume then I'd contact Panerai for there opinion. If not then perhaps wait until you're closer to the end of your warranty. Set a reminder on your calendar so you don't forget and the warranty expires. (happened to me once)