How long does my saliva sample stay fresh so it can be tested by 23andMe?

I am thinking of doing a 23andMe DNA tests and I was wondering how long does my saliva sample stay fresh or variations in temperature can affect the sample.

According to Genotek website information on DNA collection Test Kit’s a 2ml saliva sample remains stable for years if kept at room temperature. Regardless of vendor, most oral DNA buffer preservatives will keep your saliva sample stable. The special buffer in the cap of the vial preserves the DNA for transit. If the sample is unusable 23andMe will send you a replacement.