Let the amount of XP rewarded and time between cooldowns increase depending on our sailing level so that as we level up, we can spend a little more time AFK'ing.
For example:
Level 73 - 1 minute cooldown, 250xp
Level 78 - 2 minute cooldown, 500xp
Level 83 - 3 minute cooldown, 750xp
Level 88 - 4 minute cooldown, 1000xp
Level 93 - 5 minute cooldown, 1250xp