When I was putting the su's back together, I put a bit of grease on the needle to lube it. But, it occurred to me that may not be a good idea, because any grease stuck in the nozzle or on the needle will affect the mixture profile. It seems like the fuel will dissolve the grease pretty fast. However, the precision of the needle ground makes me think it might still have an effect that will decrease over time. Further, it seems like a non-oil-based lubricant could have a long lasting effect on the carburetor performance.

Does anyone have any thoughts? Am I missing something?

You should not grease the needles for the reasons you mentioned. Also if they are adjusted correctly, they will not touch the sides of the nozzle.

If it starts, the gas should get rid of the grease pretty quickly. As you said, gasoline makes a pretty good solvent.

The most I've ever put on needles is Dykem to check that they are positively not rubbing on the jet.

As stated above, they are a non-contact moving assembly, therefore no 'assembly lubrication' is required.

Furthermore, they are both non-corroding materials (brass) so no 'preservative' should be required, other than a slight coating of storage oil like 3-in-1 or 10Wt ND before bagging and shipment.

Any thick bodied substance has absoltuely no reason tobe anywhere near the inside of those assemblies.

I have seen people grease the outer sliding portions of the Jet Assembly, though, and I don't think that is unacceptable at all. White Lubriplate 630AA or other Seal-Compatible Lubricant might keep choke-application wear to a minimium, and make actuation for startup really nice and smooth!