50-55% is considered standard. Too much higher than that means you are folding too many winners, while lower than that means you are going to showdown too often (i.e. not folding on earlier streets when you should). Also, the answer depends on the stakes you are playing. At the .02/.04 stakes, with 7-10 players per flop, you are bound to face many more river miracles that hit weak draws, sucking out on your strong hands.
On another note, congrats on your winrate. I myself play microstakes fixed limit, over 75k hands at .10/.20 and .25/.50, (winrate over 1BB/100 hands, was 1.5 but just hit a 300 BB downswing, LOL) so I've made a decent bit of money at it. I look forward to future FL discussions with you, it seems FL is relatively quiet around here.