Why the timeout to PSTN call is default to 10 seconds?

We have a contact centre built on UCMA conferences. Some of features requires dialling out from conference to a PSTN destination via back2back. Sometime the PSTN destination fails to answer the call but should follow the forward no answer rule going to the person's voice mail. A lot of time this scenario fails because Lync cancels the request before the forwarding kicks in. We did some research and raising this timer "FailOverTimeOut" would fix this issue:

from OutboundRouting.exe.config
<configuration>
    <appSettings>
     <add key="FailOverTimeout" value="10000"/>
      <add key="MinGwWaitingTime" value="1"/>
      <add key="MaxGwWaitingTime" value="20"/>
      <add key="FailuresForGatewayDown" value="10"/>
      <add key="FailuresForGatewayLessPreferred" value="25"/>
      <!-- Valid values are between 5 and 600 -->
      <add key="HealthMonitoringInterval" value="300"/>
      <!-- Valid values are between 60 and 3600 -->
      <add key="GatewayStateReportingInterval" value="1800" />
  </appSettings>
</configuration>

The question is why the default value for this timer is set a value so small(10 seconds) while a lot of forwarding no answer rule would be greater than this number. Is there any risk involved in raising this timer?

Thanks