It all depends on how the network operators want to release the shows. Some will be available even before the current episode starts some will take two to three weeks to be released. Others will wait till the current season is over before it releases episodes to force you into watching them and the commercials.
In a couple weeks I am dumping the cable services all together and bumping up my internet speed. The on demand is nearly worthless and rarely does it function correctly and the regular cable service is not much better.
Last time I bothered to look at it, CBS wasn't even one of the networks listed and none of them had them had HD versions. Usually if I miss an episode and forget to record it, I just watch it online at CBS' website.
Since CBS is apparently on it now, I might check it again.