Depends on the channel, the day of week and time of day (and the time zone its main constituency resides in) and how long you waited. There are a few channels

Depends on the channel, the day of week and time of day (and the time zone its main constituency resides in) and how long you waited. There are a few channels I know that are mostly active over the workweek in US pacific time. Others that wake up with the EU, with some extra activity on weekends. But yes, some channels really are slow and mostly wake up only on specific actions (eg. joining, asking for a question, people answer, everybody gets back to doing their work) - essentially support channels.