I think it really depends upon your personality. I weigh daily but am always aware that there are salt & hormone & water fluctuations that might cause drops & gains and so I just keep a mental note and don't worry about gaining one day, knowing it will go down over the long term. For some people seeing any gain at all is demoralizing and throws them off track into binge eating, so if you have that kind of worrying/obsessive personality then weekly is probably better.