Sure you can take long breaks. There are people on this board who have multiple RTW tickets open at one time, say one traveling E-W and one W-E; who put together their trips according to which ticket has the next appropriate segment. (Lots of reissue fees likely but still cheaper than straight J.)

BTW today's Sunday Seattle paper ran a reprinted article from the WSJ about RTW travel. Our little secret is getting out. I'll post the link when it's available.