The time for inventory has been reduced substantially in version 7.5 SP1 of VMM and later, this will effectively reduce the amount of time for inventory to complete. As an example, testing showed that, before the fixes were added in 7.5 SP1, a scheduled inventory task previously would take around 2 hours 6 minutes, to collect inventory against approximately 183 ESX hosts (1 vCenter and roughly 2500 VMs). In 7.5 SP1, the was time reduced to around 43 minutes.
Alternately, you can increase the VMM Task Timeout value. The steps to increase VMM task timeout value:
1. Go to respective task folder in Jobs and Tasks, like Inventory, DeployVM etc
2. Right click on that folder and select Export option.
3. Save the task xml file.
4. Change ‘maxMinutes’ value from 60 to sufficient time like 120 in two places in that xml file. In one case, the customer put in the value of 600, essentially telling it to wait 10 hours.
5. Import the same xml file to back to the same task folder by right-clicking.
6. Re-run the respective VMM task