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I think this package called message_filters can achieve this behavior quite easily.

The TimeSequencer filter guarantees that messages will be called in temporal order according to their header's timestamp. The TimeSequencer is constructed with a specific delay which specifies how long to queue up messages before passing them through. A callback for a message is never invoked until the messages' time stamp is out of date by at least delay. However, for all messages which are out of date by at least the delay, their callback are invoked and guaranteed to be in temporal order. If a message arrives from a time prior to a message which has already had its callback invoked, it is thrown away.

(...)

The C++ version takes both a delay an an update rate. The update rate determines how often the sequencer will check its queue for messages that are ready to be pass through. The last argument is the number of messages to queue up before beginning to throw some away.

message_filters::Subscriber<std_msgs::String> sub(nh, "my_topic", 1);
message_filters::TimeSequencer<std_msgs::String> seq(sub, ros::Duration(0.1), ros::Duration(0.01), 10);
seq.registerCallback(myCallback);

I highlighted the important bit about possible throwaway messages.