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Hmmm...in the forums of another distro for users tracking Sid, the suggestion is just the opposite...do not upgrade on a daily basis.
I'd say it depends what you want to achieve:
(1) You don't like to spent time upgrading your system: So d-u on a monthly basis or less. Note: This is ***NOT*** recommended, although in most circumstances there won't be problems. But you may miss dozens of little changes or big package transitions which then accumulate to a mess. Noone may help you then.
(2) If you want to minimize your efforts, then d-u once, twice within two weeks. You'll be fairly safe.
(3) You need to be informed instantly about the changes in Debian/Sid (because you are a developer, a siduction mod or somehow interested in what's going on). You will d-u on a daily basis (maybe faking it by using the -d option). Or at maximum 4 times a day.
Whichever option you chose, in each case you should read carefully the apt-get * output (removed packages). And you should read the update warnings in the forum.
I am fakeing d-u daily and really dist-upgrade once/twice within two weeks. This way I'm always informed whether or not there are d-u problems. It's easier to then select a moment when all or most conflicts are solved in one way or another.