Is incubation absolutely necessary for alcohol precipitation of RNA? - I'm doing HIV RNA isolation from plasma. (Dec/15/2008 )

I'm working on a very sensitive quantitavive PCR (sensitivity down to 1 copy/ml) of HIV RNA from patients' plasma.

The protocol from a published paper doesn't mention about the incubation after ethanol and isopropanol RNA precipitation.

Is incubation always absolutely necessary? Or sometimes not?

When I extract RNA, I do not incubate and my RNA turns out fine