The main considerations for deciding the lock duration are:
1) How long a delay are you read for in case of failure?
2) How long does it take to process a message?
Assume you set lock duration to 5 minutes, then lock a message and your processor dies. This means that message will be available to the next receiver after 5 minutes. If there is no failure and you complete or even abandon the message then it will be available right away.
Assume you need mostly 1 minute to process a message, you can set the lock duration to say 2 minutes and not have to renew locks but if you need 10 minutes to process then you will need to call RenewLock appropriately. So if you do not care much about the first case (latency in case of failure) and want to avoid renewing locks where your message processing can always complete in 5 minutes then choosing 5 minutes all the time is fine.