I think there are enough "subjects" around to do a research job on
the topic of list moderation.
 
I suggest you rethink the notion of excluding those with less than
six months of experience. I'd guess that they will provide good insights
into the "difference" of expectations and perspectives between novices
and experienced listserv moderators/owners.
 
You would also need to consider the issue of including/excluding those
who are owners/modertors of any particular brand(s) of mailing list
servers. Each "brand" provides more or fewer features to be considered,
used and configured, and each therefore leads to potentially exclusive
and alternative experiences.
 
And, there is the issue of distinguishing the several "types" of lists.
Purposes/goals/objectives are different, and the modus operandi varies
among lists. So, all list owners/moderators are not equal, i.e., they
may not be of the same population, of the same phenomenon, unless you
are careful about how you define them. But, of course, that's part of
the fun and of the research problem, isn't it.
 
I'm not sure how well the topic can be handled as a doctoral
dissertation (even though it is surely a valid research topic[s]); that
is going to depend completely on the attitude/position/help of your
dissertation committee (and on you, of course).
 
Peter R.