I'm a bit of and oddball here in that I think once a week is the way to go in the absence of gears, depending on your level of fitness. I've seen great results personally and professionally hitting things
very hard once a week. Once a person has been at it for quite awhile, then maybe twice a week, but it just depends on how it feels. If you can handle it great, if not wait until you can. Typically when I do go to twice a week, the 2nd day is designed to be less harsh than the first. You can find some good information in the stickies from cowpimp. Here's one of the
links.