Extended spells have their duration doubled, lasting twice as long as normal.
It seems that currently, spells only double the scaling caster level portions of spell, and not the potm-specific bonus. (A caster level three casting magic weapon would last 9min, and extended lasts 12mins, rather than doubled 18min)
I was also curious on the spell description regarding Ray of Hope, It says 1 Turn + 1 Turn, which is a little weird for a way to write 2 Turns!.Was this suppose to have a longer duration, or is it kept at 2 Turns and the spell's description was a not-quite typo