Please never, ever!!
F2P is just an illusion, a soap bubble, smoke in the eyes... for us players, and for game companies as well.
It ends with servers full of always fresh new few-hits-players, this gives game companies the illusion they have more players playing the game... but the truth is that very few stick to the game after f2p conversion.
MMORPGs players just need continous content delivering to satisfy their (ours ) addiction and keep on subs, just that!