Think about your monthly usage
Estimate how much mobile data you normally use and which international destinations you call most. Someone who mainly uses Wi-Fi may value a different plan from a heavy mobile-data user. Likewise, a long international destination list is not useful if your most important country is excluded.
Before paying for a long-term prepaid package, compare the effective monthly cost with shorter plans and verify what happens at renewal. Keep the plan terms you relied on when activating service.