I was just thinking the exact opposite. I am really not convinced that the site can be maintained indefinitely for a $15 one-off payment per user. And when it inevitably closes down I will feel cheated out of the "lifetime" of service I paid my $15 for, whereas I would have been happy to pay $60 a year for it. ($5/month would also ring alarm bells for me, even though the total price would be the same.)