1. A method with regard to a library of virtual machines (VMs) on a computing device, each VM stored in a halted form in such library for retrieval from the library and re-starting on a host computing device, each VM in the library being a software construct that when re-started on a host computing device emulates a hardware system, each re-started VM including a plurality of software constructs, at least one software construct of each VM in the library being non-current and requiring a software update, the method comprising, for each VM in the library: retrieving the VM from the library on a periodic basis and re-starting the retrieved VM on a maintenance host computing device having access to at least one update source but not having access to any host computing device; allowing each non-current software construct of the re-started VM to be updated at the maintenance host computing device by obtaining the required software update from a corresponding update source as at least one patch; and halting the updated VM and storing the halted VM at the library to await retrieval and re-starting at the host computing device.