Add vm to vapp without modifying the lease time.

I am trying to add a vm to a vapp but I don't want to modify the current lease settings.  I need to power up the vm and ensure the customization runs.  The only way I can do this that I know of is to use the .deploy() function but that requires specifying a runtime lease in seconds.  I am planning to try and figure out how many seconds are left in the current lease and re-applying them afture I run the power on and forceCustomization but I am hoping there is an easier way of doing this and I am just overlooking it.