It is not about how fast you update. It is more about how consistantly you're updating. If your readers know you update every friday or every monday in every 2 weeks... (Just some examples) They mentally prepare for this and they won't find it as dissappointing to wait. I'd suggest to plan for yourself WHEN you'll be updating and letting your readers know when that day is. If you stick to it you'll notice your readers will stay more involved and active, but then again most people subscribe only when it's completed. I wouldn't necessarily say you'd need a co-author, but then again I don't know what your situation is.