When overtaking a truck, it is not necessary to immediately return to the right lane if you plan to continue overtaking, **unless a vehicle behind you is traveling at a higher speed**. This is because:

- **Facilitate overtaking**: If a vehicle behind you is going faster, you should allow it to overtake without obstructing its maneuver. This means that, in such a case, you should return to the right lane to avoid interfering with its overtaking.

- **Safety and traffic flow**: Staying in the left lane unnecessarily can obstruct traffic and create risky situations, especially if there are faster vehicles behind.

- **Overtaking rules**: After overtaking, you must return to the right lane as soon as it is safe and without forcing other drivers to change their speed. However, if there are no faster vehicles behind, you can remain in the left lane if you plan to overtake again.

These rules ensure that traffic flows safely and efficiently, allowing faster drivers to overtake without issues.