If either the bride or groom is getting married for the first time, they celebrate with sheva brachot all seven days.
If both the bride and groom are marrying for the second time, sheva brachot are recited only on the night of the wedding. The last brachah, Asher Bara, can be recited for three days.
Both of these laws are brought in the Shulchan Aruch, Even Ha'ezer 62:6.