I intend to rename several machines to be more detailed about their location.
The trouble is that I don't know exactly how long of a hostname is allowed.
What is the maximum length for a Windows XP hostname?
NETBIOS limits the name length to 15 characters. You give the computer a longer hostname (which is fine with Active Directory since it uses DNS, not NETBIOS) but the NETBIOS name will be truncated.
This KB Article lists the limits, which shows 15 chargers for NETBIOS names and 24 for Active Directory host names.