I upload one page at a time, twice a week - Mondays and Fridays. I've picked this schedule because it's one I can consistently keep up with, and still have a buffer in case of emergencies.
While several pages per update is nice from the reader's point of view - they get more of the story in one go! - it's not something I feel I can realistically pull off, so I don't. I am considering going back and editing previous episodes, collapsing them down so that I have multi-page episodes, and therefore fewer episodes per chapter - to make navigate my archives easier on new readers.
Also, if there are too many pages in a single episode, I find the endless scrolling a bit tiresome - and also confusing. When there's only one page (or one 4-5 panel strip) in an episode, I can keep track of where I am easily. If there's, like, 10 pages or more in an update, it's easy for me to lose track of where one scene ends and another begins, etc. This is, of course, purely a personal preference, so you might feel differently.
As for updating only once a month... Some people do that, and manage just fine, but remember - if you only update once a month, your comic only shows up in the Fresh-section once a month. Updating more frequently means more exposure to potential readers browsing that category.