IMHO, bibtex should now generate keys such as Hoek2006a and Hoek2006b or authoryear references like Hoekwater (2006a) and Hoekwater (2006b), but it should not (!) append the "a" and "b" to the years in the bibliographic list itself. But I may be wrong here - what do you and other users say? Should the (2006) in the example above come out as "(2006a)" and "(2006b)"?
At first I was sure that (2006a) and (2006b) are the right answer for the list. Othewise how else could the user know which entry to look up when they see, say, Hoekwater (2006b) in the text? But I just figured out the answer to that question: Users count 'a', 'b', ... starting with the first 2006 entry. However, I still don't think it's a good idea to make them do that. Let's not ask users to do what computers do very well (counting)!
And as I was suggesting: if you use numered references, I think it would be best to just switch maybeyear off completely, so my suggestion would be to have a switch "maybeyear = on/off" for the \setuppublicationlist.
Let me know whether I'm understanding it correctly. If you have a numbered reference list, then the year can still end up with a letter tag, e.g. 1. Taco Hoekwater. JournalA. 2006a 2. Taco Hoekwater. JournalB. 2006b Ah, I hadn't thought of that problem. You're right, there shouldn't be a maybeyear in this case since the list number disambiguates the reference completely. -Sanjoy `Never underestimate the evil of which men of power are capable.' --Bertrand Russell, _War Crimes in Vietnam_, chapter 1.