Just fooling around today doing some simple math based on my net worth I came up with the following:
I have 350 billion ISK and 12 accounts
With PLEX at 550 mil each, 350 billion / 550 million is enough for 636 months worth of account subscriptions.
With 12 accounts, 636 / 12 = 53, enough to sub one account for 53 years or all of my accounts for 53 months (nearly 4.5 years).
If one were to pay real money for 636 months of subscription time at $19.95 per month it would cost $12,688.20
My accounts are worth more than I thought, maybe I should start playing this game seriously!