Actually GDPR requires you to delete data when no longer needed. How long data is needed depends on what type of data it is. For example financial transactions

Actually GDPR requires you to delete data when no longer needed. How long data is needed depends on what type of data it is. For example financial transactions are covered by other laws to be kept for certain amount of time. If data is linked to a survey that is completed then, by law, that data is no longer needed and should be deleted. How long should photo likes and comments be kept? I don't think there are good guidelines or judgements regarding this but it is nevertheless something to take into consideration and in most cases delete data based on age.