If I top up my eSIM data, does the validity extend?

Yes, topping up your eSIM extends your validity period.
Each top-up comes with its own validity window, which starts from the day you top up. For example, if you bought an eSIM with a 7-day validity and topped up on day 4, your data will no longer expire in 3 days. Instead, a new validity period (such as another 7 days) begins from the top-up date.
This allows you to keep using your eSIM without losing access mid-trip.