Since I've got a busy life I can't stay always connected to Messenger. That's why, for example, I write that if someone wants to contact me to buy some software, it is better if he sends me an email rather than adding me on messenger. Via email I can provide a better service and I usually check the inbox everyday.
If I don't access Messenger for few days as soon as I open it again I receive many offline messages like this: "Are u here?"... If I am offline it means that I am offline, so no, I am not there. Again, instead of sending offline messages, send me an email and you will be answered.

Regards