Prestige really doesnt worry me, after 3 years, 4 in april i think, ive hit 30 mill prest, 5-6 mill of which was gained from trebing a hero, and ive left alliance a total of 3 times and lost 10% prest. First time lost about 40k prest, next time a mill prest, next time 2.4 mill prest. first time was cause my alliance was dead, 2nd and 3rd time were to give a city to an ally while no presbyters or up were on.