Hajj is obligatory once. Repeat Hajj is permissible but contemporary scholars debate its advisability when millions await their first opportunity.
Hajj is obligatory once in a lifetime. Additional Hajj is voluntary (nafl) and carries significant reward. The Prophet was asked about performing Hajj every year and indicated it is meritorious but not required.
However, with millions waiting for their first Hajj, many scholars argue repeat pilgrims should give way to first-timers. Saudi Arabia now officially prioritizes first-time applicants, and some countries restrict repeat applications within five years.
A balanced approach: if your repeat Hajj does not deprive another Muslim of their first opportunity and your finances allow it, voluntary Hajj is blessed. But yielding your slot to a first-timer may carry even greater reward.
Source: Ibn Qudamah, Al-Mughni; International Islamic Fiqh Academy