Not Weekly

It's never an absolute is it? The economic news is both good or bad. Those pesky radicals give you a positive and a negative. Effect's both a noun and a verb. A comic can updated infrequently without problem.

Book and chapter based webcomics can get around the flaws of a slow update schedule. The size of each update replaces the context produced by a more serial comic. The relevant background and character traits can be picked up again--an entire story provides pleanty of time.

Sustaining reader interest as much of a factor either. There's no missed updates, each chapter comes out whenever it's time. With no firm updated schedule there's no reason for readers to visit regularly. No loss of readers when the expected update doesn't show up. A mailing list or other notification system works fine.

Depending on the content, a comic may even work better updated in chunks. Frequent delays can leave the story hanging. Much better when the author can decide when the story can stand a break. Similarly more time can be taken for the details (both touching up the artwork and editing the plot). The longer deadlines provide more time to find and correct errors.