I encourage all of my learners to have at least one lesson in the evening (when it is dark) to gain some experience of driving in the dark. However, I do not feel that this should be planned until there is sufficient competence in the basic skills (when driving in the daylight).
During the spring and summer months, I have regular evening lessons (often with learners who are not available during the day). However, as it is now getting dark before 7pm and will be dark by 5:30pm when the clocks go back at the end of the month, I am no longer taking on new pupils who only want evening lessons. Therefore, I will now have more availability in the evenings for my learners who want a session of driving in the dark.