I am in process of installing some new recessed lights in my kitchen. The house is an old farm house built in the late 1800's. Some of the wiring is the old cloth wiring (which I will replace) but some is the somewhat newer wire that has a silver colored insulation covering. The lights I am considering indicate a 90C temperature rating. I was told that this came about some where around 1986? I doubt that this older wire meets that requirements. Is the 90 C requirement for all wiring servicing the light circuit? - meaning I have to replace all wires for the switches and lights. Or is it only for the wire that is directly inside the recessed light canister?

This has been a problem to deal with in the electrical industry, you must not allow the old wire into the junction box of the recess fixture. You actually can let a junction box float in the ceiling cavity splicing onto new 90Deg rated cable, say a couple of feet is plenty, instead of replacing all the cable.

Just be sure to make good tight insulated splices.