(For) months; emphasizes that something continues for many months.
彼女は何ヶ月も入院していたが、やっと退院した。
She had been hospitalized for months, but finally got discharged.
この不調は何ヶ月も続いているので医者に診てもらったほうがいい。
This problem has been going on for months; you should see a doctor.
契約の更新が遅れていて、何ヶ月も給料が支払われていない。
The contract renewal has been delayed and wages haven't been paid for months.