The circle is a time when everyone comes together and we make decisions about the tour together by consensus.
More about the structure of a circle is written in the chapter about consensus decision making.
There have been Biketours where one short circle happened every morning and evening, but in recent years circles rather happened every couple of days. It is good to have a circle at least every 3 or 4 days, otherwise, more and more things need to be decided informally, which always excludes people from the decision.
It can be good to have a small informational circle every morning where things like the route can be announced. Part of it can be everyone expressing their cycling needs for the day. The difficulty with circles on cycling days is that they can only happen in the morning (where some people like to sleep) or in the evening (where some people like to sleep). One solution is to write the information down, so that those asleep can read it later.