Mandamados can be visited year-round, but the most atmospheric time is the feast of the Taxiarchis on 8 November, when the monastery draws pilgrims from across Lesbos and the Greek diaspora. The village fills up, the monastery courtyard is packed, and the normally quiet roads become very busy — it's worth seeing once, though accommodation in the area will be scarce.
For a quieter visit, spring (April to June) is ideal — the countryside around the village is green, the sea is warming, and the rest of the island is not yet crowded. Summer brings heat and increased traffic to Lesbos generally, but Mandamados itself stays relatively calm. October is pleasant for walking the northern coast roads.