SA cached timed out?

[Ken A]

hmm...

In the log:
Oct  3 22:26:27 server MailScanner[15463]: SpamAssassin cache hit for 
message k945POHg026840

In the msg header:

MailScanner-SpamCheck: not spam, SpamAssassin (cached, timed out)

Is the SA cache saving 'timed out' results? I'd rather it not do that. 
There must be some room for improvement here?

Ken A.
Pacific.Net