Live Link doesn't specifically enforce a limitation, though downstream systems and connections do impose limitations. I believe this limit can differ from country to country. Therefore, it's best practice to limit the number of characters to a reasonable number.
If you have a use case that you could provide more detail about, we can consult with our experts in that region to discuss best practices based on your use case and country.
I figured that the concatenation processing would be more of a downstream function, since I understand specific carriers and connections all need to support longer messages/higher character counts in order for it work. To keep the discussion from getting too complex, lets assume we're using UTF-8/GMSC characters in the message body and sending to +1 destinations - US & Canada.
If I am sending message of say, 500 characters to a mobile handset via Livelink, how does it work within Livelink & in downstream systems to manage the request?