It is preferable to bottle as soon as the gravity has stabilised, but leaving it in a fridge for a week can help clear and condition your beer if required.
If you leave the beer too long you have a higher chance of the yeast cells starting to break down in your beer (autolysis). This breaking down of cells releases the contents of the cells into your beer (this can include off flavours processed by the yeast).
Autolysis is often perceived as a 'meaty'/'sulphury' flavour to the beer.
How long this takes depends on the shape of your fermenter.
- In conical and tall narrow fermenters, autolysis will occur faster due to the increased pressure on the yeast.
- Whereas wide and flat bottom fermenters autolysis will take longer to occur due to the relatively low pressure on the yeast cells.
It is not recommended to leave the beer on the yeast for more than a month. However, by dumping the yeast (conical fermenters) this time can be extended. In the case of mixed culture sour beers, the other microorganisms in the beer consume these products and therefore mixed culture sour beers can be fermented for years.