In the past, LINE had officially mentioned that it stores data for a two-weeks storage period. However, that statement has been removed now. So, it is not clear what is the exact retention period offered by LINE. For Keep, the files are kept for 30 days if their size is larger than 50 MB. Once the storage period gets expired, it will not allow you to access photos/videos again. Therefore, it is recommended to save the important photos/videos and other attachments as soon as possible.