I wouldn't pay too much attention to those guys who don't write you back for too long. What I usually do if the guy doesn't write me back is I would wait for a month or so, and send another mail (because despite being RJer, we all still have a life outside of RJ). And if he doesn't write back after that (after reading it), then just send him to the island of lost men and move on with your life. You have bigger fishes to fry (I hope).
I do want to make one distinction though, and that is: you don't need to talk to a fellow RJer like, every single day, or even like every week, and I'll tell you why not:
1) You'll be too emotionally invested and attached, which is a horrible idea. You're setting yourself up for potential heartaches. Why do that to yourself?
2) You want to pace your online "friendship" so you don't actually run out of stuff to talk about. Slow and steady is the key. Most of the guys that I still talk to on regular basis, I normally receive 1-2 mails (pretty long ones) per 1-2 weeks. And this is different from the initial 5~10 mails per day during the first week or so. That's the "honeymoon" period, and it's perfectly normal for the rate to go down after that. Hopefully you have already gotten to know this guy in a pretty substantial way. So in the future when you check in, you'll be able to carry the conversation for like another several exchanges back and forth.
*disclaimer: this obviously differ from person to person. There are several members on RJ who prefers IM-ish style of conversing, and that's ok. I usually tend to go long since I am a chatterbox.
3) Now, if you do have a secret crush on this guy (I'm not saying you are, I'm just bringing this up for RJ general audience who actually read my posts), my suggestion is to treat him as a friend as you normally would. Don't pay too much attention and get your head all wrapped up in a fantasy, because after all, it is the internet and you really shouldn't take this stuff too seriously. Especially gay internet, where practically every single guy on RJ has GayDHD.
Hope this is helpful