Question 1 - My answer is post #5
http://www.fatjockey.com/forum/showthread.php?14912-Free-Bets - there are no FREE bets, absolutely. However, it also isn't the same as using real money - it absolutely depends how you acrue them. If you get £10 every time you place £50 of bets, that is not the same as getting "money back as a free bet" etc.
Question 2 - They could remove the option at any time - my theory on that is to make hay while the sun shines. It definitely isn't a stategy I use to make money consistantly (if at all really), but it does mean when you get things wrong or circumstances change, you can be ahead of the curve. If I come on here, learn a horse is out (often quicker than the bookies do) I would cash it out. I definitely did that last year....