How long can you leave your brew in the primary fermentor?

I've already brewed and bottled my first Ale (Tom Caxtons) however I've started another kit (Coopers Lager) and I'm intending to keg it in a pressure barrel this time, along with a few bottles of it.

What I'd like to know is how long I can leave it in the primary fermenter without moving it to the next keg, or bottles. The reason I ask is I've been into my local store to get a pressure barrel today but they've sold out and I'll have to wait a week or so and wondered if it's OK to just leave it in the primary fermenting barrel with the air-lock on it.

Cheers

Carl

Many of us leave our beers in primary for a month then bottle (skipping secondaries.)

A few folks have left their beer in for 6 months with no problems.

Revvy said:

Many of us leave our beers in primary for a month then bottle (skipping secondaries.)

A few folks have left their beer in for 6 months with no problems.

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agreed. My standard is leave in primary for a month, then rack to keg

Revvy said:

Many of us leave our beers in primary for a month then bottle (skipping secondaries.)

Click to expand...

If I leave it for say a month, then add it to a pressure barrel do I simply add CO2 cartidges to the barrel or would I need to secondary sugar it to get fizz?
With it being a lager I want a fair bit of carbonation to it and if I leave it for a month or so in the primary would that not render it flat so I'd HAVE to add either sugar or CO2 to it?

Thanks for your help folks