One long plan, or repeated short ones?

Just once — installed before departure or right on arrival, then used continuously to the end of the trip with no need to touch the settings menu again.

The repeated short-plan route usually loses less, since you simply stop buying the next one. A single long plan already paid in full typically cannot have its remaining days refunded under usual terms.

Yes. You can buy and install the new profile in advance without switching that line on, then switch over once the current plan is nearly or fully spent. This shortens the time without a connection.

Not always — it depends on the specific plan. Check the order page before buying to see whether a renewal or top-up option exists. If not, buying a separate new plan to follow on is always still possible.

No. Every phone stores a limited number of profiles. If choosing the repeated short-plan route, delete expired profiles periodically so a new one never fails to install on the day it is actually needed.