Only twice for me.
First time was on Konami's Lucky Fountain at OLG RCR. Got 255 free spins on December 10, 2015 and rode it to a 395x win. Second time was on NextGen's King Kong, where I got 100 + 100. Didn't do so well, barely 200x.
Having played this a fair bit, I am actually not that surprised. You actually did OK there (and I
am being serious), because it's quite hard to average a win of 1x per spin on long FS rounds for this game, even in a short round. The reality is that the base game is quite poor, although there is big win potential from getting a 4OAK or 5OAK of the blonde girl with a King Kong Goes Ape activation. But because there is no King Kong Goes Ape within the FS round, that has an impact. Enough of an impact to mean the 2x multiplier during the FS round doesn't do much to help you average a win of above 1x per spin. The big wins (250x and above) in this game come from getting
really long free spin rounds. And 200 doesn't qualify as long...not on this game.
If you want to win 500x, chances are you will need more than 450 spins to achieve it, maybe even 800.
Here's all my 100x wins on it - with the length of the round in brackets
866x (1,050 spins)
538x (400 spins) Best average - 1.345x per spin
497x (750 spins) Worst average - 0.66x per spin
496x (450 spins)
365x (450 spins)
217x (225 spins)
143x (150 spins)
Only 2 of those 7 rounds had an average of over 1x per spin. In one of those two rounds, I got a 4OAK of the blonde girl.
In the other, I got a 5OAK of the bloke. Those are the two biggest wins you can realistically hope to get in a FS round.
Unless you get a 5OAK of the girl or get 5 scatters (both pretty unlikely).
That's why, on the occasions I win 50 free spins, I actually reject them and take my chances on the mystery prize.
If I get 75 or more, I take the spins, because I fancy my chances of getting a re-trigger then.