To MrM
I think you left out one 'lesson learned' and that is to post regularly. If I know a story chapter is going to be available, say, every Saturday (or every Wednesday and Saturday) then I can look for it; moreover, I'm more likely to retain the story line or can be refreshed of it in a couple of paragraphs of the new chapter.
The trouble with long delays is that I have to often have to commit to rereading the earlier chapter (chapters) to remember where the story sits and who the characters are.
I suggest two approaches: 1) have the story finished and release chapters on a schedule (which is what I did with my Jake's Side and Jake's Hand and Palouse stories and a story, posting weekly at GA now, that I edited, Between the Push and Pull); or 2) a la Graeme above, have enough chapters of the story written and edited ahead (plus a clear idea of where it is going) and be able to release it on a schedule. This latter usually means that there should be four or five chapters in the "outbin" at any time, rotating one to publication and replacing it with a new, written and edited chapter.
A prolific writer with a regular schedule can have a chapter available weekly for years, all of which enhances a loyal following.