It depends. Sometimes we're doing every week day and two-a-days on the weekends and other times our schedules don't mesh or one/both of us are tired, not feeling well, we pass out on the couch watching a movie, etc. and we go without for a week or more.
As long as there are no underlying issues, an ebb and flow is normal. But if you have an issue or think she does you should definitely have a conversation about it.