I'd call it done. If its not done by now, something is seriously wrong, and its something that more time isn't going to fix.
Then again, I don't know your feedstock source or whether you have any of the new polymers in it. It is possible that you are having some problems associated with polymers, and if that is the case, your product may benefit from increasing the heat another notch or two for another four or five hours.
You are well past the point where byproduct formation should be a problem, and you have reduced anything you are going to reduce at that temperature. If you have some of the new reaction inhibitors stalling completion one thing you can do to degrade them is to apply more heat. I know this is contrary to what I have preached in the past, but in the smaller reactions I have been forced to run of late the gakks have succumbed to the application of more heat in the last part of the reaction.
I still adhere to starting with a gradual increase to temperatures and a wet start. I still think the reflux needs to be done under 120C; I just have the sneaky feeling that the new inhibitors may degrade slowly under these conditions and increasing the temps significantly after the bulk of the reduction should have been accomplished may be a final assault on the inhibitors that overcomes them. Increasing the temperature after the reaction has progressed for a good period of time may break the remaining gakks down and let the reduction complete.
I can't say that I've done this enough to verify results, but the last few small batches I've done I have raised the temp significantly several hours into the reaction, and the product has been far closer to the standards I seek than it has been without the temperature increase. After forty-eight hours, I don't think you are going to hurt the meth by cranking the heat up some, and you shouldn't be making tweaker dope dope since you should be past the stage where you make those by-products. Its speculation, but it seems to work in the few trials I have done. Placebo may be more correct than ever on this point since the introduction of the new gakks.
My best guess is that your reaction is done at the 48 hour mark. If you have serious questions about whether it is, why not take the temp up another twenty to twenty five degrees C for another four hours? I'd pull a sample now and work it up, then compare that with what you get four hours later. Your results might tell all of us something about the effect of heat at this stage of the reaction.
