assuming a person has a Schengen Visa with MULT number of entries, duration of stay for 30 days and it's valid over a year. Is the "duration of stay" limited for each 180 days a year, or is it the total amount of days, after using it the visa becomes invalid? According to the visa code
- ‘DURATION OF VISIT ... DAYS’ heading:
This heading indicates the number of days during which the visa holder may stay in the territory for which the visa is valid. This stay may be continuous or, depending on the number of days authorised, spread over several periods between the dates mentioned under 2, bearing in mind the number of entries authorised under 3. The number of days authorised is written in the blank space between ‘DURATION OF VISIT’ and ‘DAYS’, in the form of two digits, the first of which is a zero if the number of days is less than 10. The maximum number of days that may be entered under this heading is 90. When a visa is valid for more than six months, the duration of stays is 90 days in every six-month period.
This 30 days seem to be equal to 90 by default...