What scares me a little bit is that I am unsure how you came to this decision.
Because obviously this will lower your overall income, so if it was money you needed this is probably not the way to go.
Unless you really needed money NOW, as in right now.
Short term sure, you will rake in, but a couple of years from now, when most have a lifetime sub, and you have spent that cash already.
Will you continue to run this site with no revenue other then the revenue you got years before?
Aside from the new gamers coming of age.
I paid yearly, or 3 years last time i think, I have already spent more then a lifetime sub here, and I would have continued to do so, because I like that option, in all strides of life, I happily pay a bit more for the option to bow out should the need arise.
I got my lifetime now, no biggie to be honest but you lost out, on me at least, for quite a bit of cash.
Financially this makes no sense, unless you are planning to cash out.
And that is the bit that scares me.
I can understand MMO's and whatnot doing this, because their services are a bit limited and getting a lifetime or yearly sub up front makes sense for something they know probably will not be around for that long.
You guys however provide a service the need for which will never go away.
Removing the lifetime sub, aside for the people who already have it, would be a more fiscally sound decision in my opinion.