The Dude only uses the 32bit counters, the best you can do is create a new interface and set the speed to 4294967295, then it will record somewhat correctly but there will be gaps in the graph when the counter rolls over. You could lower the polling interval but you don’t want to collect so much data. Really the best thing to do is live with it until they support 64 bit counters directly. OR you can create your own function to read the OID and use rate64 to graph your own values.
Adding MIB files to the dude changes OIDs into the text for that vendor. Also values in snmp can be float, interger, double, signed, char, etc and I think the MIB has that detail too. BUT As long as SNMP is enabled you can read any OID and use it directly in a function or a probe.
If you decide to build your own probe and use Rate64 search for rate32 in the probe tread.
Lebowski