As a linguist I find it quite interesting that there are national divisions even when it comes to text speak.
The more "simultaneous" the conversation, the less likelihood that kisses will be left. Texting is mostly a non-simultaneous medium because you expect to wait some time before getting a reply, but Facebook chat isn't. The less simultaneous the medium, the more scope there is for including social niceties, because you have more time. This is why you text kisses but you don't do it on chat.
That means the amount of kisses depends not only on the social relationship between you but also the speed of your conversation. If he's in the car or on the run you won't get any kisses, if the conversation is flowing back and forth in real time you'll get less kisses...
I would argue also that kisses mean more with older texters, because they are more conservative/jaded because they have seen it all before. You may simply have an older texter, or a less experienced one, or one who has a personality opposed to putting kisses.
Verbal diarrhoea, I know, but for the record I tend to go with two kisses as a baseline. One is aloof; three is vaguely flirtatious. I also use one for male friends when the text has a social function, when the friend is professed to be a bit gay, or when it's the first time I've texted them in some time. My girlfriend and me tend to put loads, I don't know why it's just an idiosyncrasy which arose.