When someone says "just popping in to say hi again", it means that they are saying hello or greeting someone they have not spoken to in a while. It is a casual way of reconnecting with someone.
The phrase "some time" is relative and can vary depending on the context and the person using it. It could mean a few days, weeks, or even months.
The phrase "just popping in to say hi again" is often used as a friendly and informal way of reconnecting with someone. It may also be used to show that the person is making an effort to stay in touch or maintain a relationship.
The tone of this phrase is generally friendly and casual. It is a way of reaching out to someone without being too formal or serious.
It would depend on the context and the relationship between the individuals involved. In a professional setting, it may be more appropriate to use a more formal greeting or simply say hello without using the phrase "just popping in to say hi again".