In general, the beer can stay on the spent yeast for some period after fermentation has effectively ceased. If you are only doing a primary fermentation, then you need to make sure that fermentation has really stopped by taking hydrometer readings. If it doesn't move over 2 or 3 days then most the yeasts' hard work has been done.
I, like others, have left the beer in primary well after primary has finished, either because I've been away/too busy (how can you be too busy to make beer :blink: ) or whatever. If you keep sanitation under control then you should no trouble if you leave there for a week or so.
There are some nasty spoilage bugs (peddio_something_or_other and its brothers) that can start to react with fermented beer. This is because these nasty buggers can reduce the sugars that are left over because normal beer yeasts can't fully breakdown all sugar varients. Again though, if you've kept sanitation under control this shouldn't be a problem either.
If nothing can get in to infect it, then you wont have a problem, at least over a week or three. Leaving it for much longer though can run the risk of the yeast starting to eat itself (called Autolysis) and in the process generate lots of Vegemite. Opinions vary widely on how long is too long, but most certainly a few days will not present a problem.
As for oxidisation, again if the fermenter is well sealed then then there will be little if any O2 in contact with the beer, although I wouldn't go shaking it around just to prove the point.
Hmmm..... maybe I should have just said
Relax, Don't Worry - Have A Homebrew
Trev
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I was unsure whether i'd have time to rack as soon as fermentation was complete. Cheers. Cal.
