Validity on the ETravelSim Poland eSIM starts the day you begin using it in Poland, when your phone first connects to Plus on arrival, and runs for the full 30 days regardless of which data tier you choose. You can purchase weeks in advance, install the QR code at home before flying, and the timer only starts on first connection. Installing at home is the safer option because you'll know before boarding the eSIM is set up correctly. Don't delete the eSIM profile after installation — reinstallation may not be possible.