If you bought a physical SIM card, we advise you to insert it on your device only when you arrive at your destination as it might activate in your home country and start deducing your credit validity period.
If you bought an eSIM, you will need an Internet access to download it so we advise you to download it before departure but enter the PIN code only when you arrive at your destination to eventually finish activating your eSIM and make sure your credit validity period is not deduced.