Duration

Spell duration
Spell duration is the length of time a spell or effect lasts for. For spells, duration is often based on caster level, but some spells have a fixed duration (e.g. the Summon Monster spells, where duration is 10 minutes).

Since U14, many low-level spell buffs with a duration of 1/minute per caster level have a minimum duration of 5 minutes.

The Extend Spell feat can be used to increase the duration of buff spells.

Quest duration
Quests are categorized by duration (Very Short, Short, Medium, Long and Very Long - see Quests by duration). Quest duration is often based on time to complete by fastest route:
 * e.g. A quest may be categorised as Medium when there is a shortcut from near the start to the end fight, but can take much longer if the shortcut is not known/used

Quest duration has no impact on gameplay in Casual, Normal, Hard or Elite difficulties.

In Reaper difficulty, quest duration impacts reaper XP (from a multiplier of x0.8 for Short quests to x1.4 for Very Long quests).