Why do you suspect the existing 4mm banana sockets on your DMM (K2015?)?
Also, think about the thermal characteristics of the long, thin pin used to connect the lead from the PCB to the back of the stock banana jacks.
yea i did
there was a instance while cover was open, i have my finger on the pin with connector. the DMM is running and python logging. the reading ran off about 8ppm. i thought that was interesting. there is also the point where wire solders to the PCB, there should be some EMF there, and there is no cadmium solders.
so instead of gold, it should practically all be copper + some de-oxit?
How important is it to minimize thermal EMF when the case is open and you are touching things? I'd think it isn't very important at all. With the case on and the device given its proper warmup period, I'd guess that both sides of the PCB joints are effectively the same temperature, as are both sides of the switch contact points, and both sides of the internal connection to the tip of the panel jacks. Moreover, they are all paired, and the pairs are probably at similar temperatures. All of which adds up to minimal thermal EMF in actual operation, and what does exist, is mostly cancelled out.
Sudden changes to the outside temperature will upset the equilibrium. Plugging leads into the jacks will also upset the equilibrium, and take a little time to equalize. If you really want to avoid the time to equilibrate when inserting room temperature leads into the case-temp jacks, it might make sense to have some extension leads that you leave plugged in.
As for wear and tear on the panel jacks exposing the underlying copper to oxidation. It could happen. Replacing the jacks shouldn't cost much, take much time, or involve much risk. I think there is a good chance that it wouldn't make a lick of difference, but just replacing them would address your concern without the time required to test the situation. If you do replace them, I strongly suggest that you replace them with the original pin style, rather than the blade-lug style you linked to, because my guess is that the pin stretches the thermal gradient between outside temp and internal temp over a longer distance thus reducing differences between internal lead and socket temps.
Stepping back, I have a larger suggestion for your effort to improve upon the performance of you DMM. Before you break anything else inside the DMM, consider making an external measurement pre-amp that will take low-level signals and produce a suitably low-noise +-10v output that you can feed into the DMM. Once you've got that working well enough that it matches the noise and sensitivity characteristics of the 1v and 100mV ranges on your DMM, you'll have a much better idea of what it will take to hack your DMM to actually improve its performance. You might even start with the reverse-engineered Keithley 2000 schematics and duplicate the relevant parts of its front end circuitry.