AFAIK, you cannot change the default values unless you modify the code (and recompile).
I would recommend you to create a template for you endpoint. See Sample 752
For example, you can try following configuration.
<proxy xmlns="http://ws.apache.org/ns/synapse"
name="TestProxy"
transports="http"
statistics="enable"
trace="disable"
startOnLoad="true">
<target>
<inSequence>
<send>
<endpoint name="ep_name"
template="ep_template"
uri="@@To@@"/>
</send>
</inSequence>
...
</target>
</proxy>
Following is the template for endpoint
<template xmlns="http://ws.apache.org/ns/synapse" name="ep_template">
<endpoint name="$name">
<address uri="$uri">
<timeout>
<duration>30000</duration>
<responseAction>fault</responseAction>
</timeout>
<suspendOnFailure>
<errorCodes>-1</errorCodes>
<initialDuration>0</initialDuration>
<progressionFactor>1.0</progressionFactor>
<maximumDuration>0</maximumDuration>
</suspendOnFailure>
<markForSuspension>
<errorCodes>-1</errorCodes>
</markForSuspension>
</address>
</endpoint>
</template>
I hope this helps