I'm not aware of such bulletins. They may exist, but I've never seen them. I'd be surprised of Loud had much, since the amps are over 20 years old, LONG before Loud bought the SLM amp lines. If you call them and ask for a service bulletin, unless you are a service center, they won;t even bother to look up whether there is such a bulletin, because they won;t be sending one out to you even if there is, so why use up the time?
The only wiring that overheats in tube amps is generally the heater wiring. Those are the only wires that have to carry any current. And it is usually a connection that fails, not the wiring itself.
Look in your unit, is ther any wiring or conections that look like they overheated? If not, chances are it will continue that way. It has lasted 20 years without failing in that way.