Transmitters simply transmit one channel at a time. Therefore you will have a lag between ANY two channels on ANY radio period. Now, the closer the channels are in the transmission sequece the less noticable the lag will be. The lag between 2 and 5 will obviously be longer than 2 and 3 for instance. The more channels you have the longer the lag between the first and last channel. I've heard that some transmitters will transmit "primary" channels 1-4 or 1-6 twice before they transmit the lesser important (in their opinion) channels.