I have had some sucess in SA, but have deicided to check out SB. One of the biggest pluses is that, since you are not on a monthly plan, you can keep your credits if otherwise occupied, and can wait for the POTs to contact me.

So I had good beginners luck and got a 20 year old, a little pudgy,  to  go down on me and then got into missionary.  For various reasons, we never reconnected

However, since then, I have been rolling snake eyes. Usually, I wait til they message me, and then I write a nice note telling them they can continue to reach me on SB, but can text me at any time. Sometimes I boost the message and ask for secret pics or questions.

So now, going on for more than a month, I have been unable to get an POT to return my message or to text me. SA was very flaky, but at least I got a lot of texts. What am I doing wrong?

Personally I'd go back to SA. They are the largest and most established site and their membership fee is really not that bad considering what they deliver. I keep my membership current even if I'm tied up with seeing SB's and work/family commitments. Always best to keep lines in the water. One never knows what one will catch. I've heard mermaids really do exist.  

I've been on SB for a few years now.  Getting contacted by them on SB seems to be meaningless.  I get three new contacts a day, on average.  I don't have a public picture and my age is listed as 70.  So there is no particular reason they would initiate contact, and yet, three a day.  I don't know what they see on the babe side, but for some reason they blast to a lot of gents.  So those contact attempts from SB babes have no particular meaning as far as I can tell.
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Therefore I wouldn't wait for them to initiate contact, and I wouldn't assume them initiating contact means anything.  
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So I would do searches instead and just ping the chicks you find interesting.  As in life, if you are good looking, your chances improve.  I'm not good looking so I get chicks who are more interested in money than relationships.