Hac is farz once. Repeat Hac is permissible but contemporary scholars debate its advisability when millions await their first opportunity.
Hac is farz once in a lifetime. Additional Hac is voluntary (nafl) and carries significant reward. Hz. Peygamber was asked about performing Hac every year and indicated it is meritorious but not required.
However, with millions waiting for their first Hac, many scholars argue repeat hacilar 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 Hac does not deprive another Muslim of their first opportunity and your finances allow it, voluntary Hac is blessed. But yielding your slot to a first-timer may carry even greater reward.
Source: Ibn Qudamah, Al-Mughni; International Islamic Fiqh Academy