I believe the official statement is SMVI supports the same number of VMs and Datastores as vCenter. However there are some practicalities that you should consider. First, VMWare snapshots on that many VMs may not be possible. I would strongly consider discussing disabling the VMware generated snapshots which will allow SMVI to scale much better. Perhaps create seperate jobs that snapshot only the VMs that you feel need that quiecing. Second, try to minimize the number of jobs stored in SMVI, if possible try to group multiple datastores together into simpler jobs.
Backup the SMVI server folder. With that many VMs it is possible for database corruption on the SMVI server which would be a real pain. Back up the server folder so a restore is possible.