I like long exposure photography and I have practice it quite long. I have to say that in my experience Ilford films have generally much worse reciprocity failure than any Kodak emulsion I have used. I am not a big fan of Ektar, to be honest I donīt like it at all, but I expect Ilford table to give overexposed results, when used with for it. The best way is to make tests and check the exposure and the color rendition. It seems like Ektar tends to shift more to cyan when used for very long exposures.
Here is a link for an old APUG thread: