The only freeplay you will get from CET is if you book an offer to stay at a CET property that includes freeplay. Actually, if you're looking for small freeplay, various casinos (I know the Linq usually has it) have big slot pulls you can do if you earn a certain amount of Tier Credits in a day (usually 10ish). You spin that and can earn like $5 in freeplay (a bigger prize of like $100 is listed but doubtful)
For me I get free-play on offers for my next stay based on previous play. My 300 in free-play on all my trips last year dropped down to 150 at the beginning of the year, and then down to 40 this past month even though I haven't changed my play. I just reserved a room for September and noticed a 250 free-play offer of which I'm taking advantage. I'm staying Saturday to Monday, and they told me that I can get that offer because I'm staying until Monday and not just the weekend. I used to get the 300 free-play offer for any nights I stayed.
It is all based on PLAY. Sometimes they do a teaser for new players for a few bucks, but any serious freeplay is tied to your past play. Keep in mind what they are doing. They hope that whatever they give you is enough to get you to not only visit, but to play that and much more, giving them more money in the end.