Dima, thank you again. It's slowly starting to clear up.
A couple of questions are arising now:
1. you said that I should set the Media Set to be created the day after I am going to export the media; since I plan to export on Fridays, I should set the Media Set to be created on Sundays. However, the manual says that if the tape where data should be written is not available, VBR creates a new Media Set automatically. So couldn't I just set "always continue the same Media Set" and just export the used tapes on Fridays? Then VBR should create a new Media Set not finding the last used tape available.
2. The plan "always export tapes on fixed day of the week" in some cases could not happen. Say that tapes are normally exported on Fri., new Media Set and Synthetic Full are created on Sat., but that Friday is a holiday. If the tapes are then exported on the previous day, a new Media Set would be created on Friday and another on Saturday? What would then be the best strategy?