It's not clear what your question is; you can use a custom ReleaseStrategy to release on whatever algorithm you want. e.g group size >=2 and time since last arrival > 1000ms.
Of course, this might release at 2 when #3 might arrive 1ms later.
It is important to understand that the release strategy is triggered by message arrival (aggregators are passive). That's where the reaper comes in.
If you can explain exactly what you want, we can try to help. But, reading the above, I hope it's clear you can't have an algorithm "group size >= 2 and last arrival <= 1000ms ago and next arrival won't be in < 10ms".
However, if the message producer knows the sizes of the groups then simply have it set the sequenceSize/sequenceNumber headers appropriately and you can then use the default strategies.
Gary P. Russell
Spring Integration Team
SpringSource, a division of VMware