invocation service - keep alive

we have clients connecting to our invocation service running bursts of (batched) trade puts. This is a low latency operation and we warm up jvms and do test trades etc once they connected for the first time to keep the latency low for their first trade put

However some clients connect but use this service infrequently (ie once every few hours) but even so the latency should be within the agreed SLA.

we have noticed long latency for their first batch if client goes quiet for a few hours. 

is there any config on invocation service that we can use to keep the connection alive