I mean no disrespect but it does not sound like you fully understand the Worksets options .
With large models, we tend to choose the 'Specify' option to choose a only Worksets which do not have linked models to be loaded (open). We find that excluding those Worksets which hold Linked Models helps to speed up opening the model initially, as it doesn't have to actually load the linked models themselves.
Once the model is open, we then open the other Worksets that we need to via the worksets window by simply changing them from 'Closed' to 'Open.'
The 'Last Viewed' option will (I believe) open the Worksets which were open during the latest Synchronise with Central.
Worth checking the Autodesk documentation on this subject first, I would say:
Help | Open Worksets | Autodesk