Hello Golan,

according to Neflow command reference

http://www.cisco.com/en/US/docs/ios/netflow/command/reference/nf_01.html#wp1013625

active

Specifies the active flow timeout.

minutes

(Optional) The number of minutes that an active flow remains in the cache before it times out. The range is from 1 to 60. The default value is 30.

you cannot specify a time less then 1 minute.

However, I wonder if this makes sense the flow cache needs to store active flow for some time. Of course the table has a limited size and to avoid overflow it can be wise to reduce the time an active flow uses one entry in the cache but the lower limit is 1 minute.

Hope to help

Giuseppe