I have held a Secret clearance now for 2 yrs and am being upgraded to a TS, not a whole lot has changed since my last investigation. Especially with the Covid pandemic (no travel) or any other significant changes in my life. Would I just mirror my last SF-86 that I filled out since nothing has changed since my last investigation?
I was in the same boat just a few months ago, upgrading from S to TS after 2 years.
I thought that nothing much had changed, but I went through line-by-line to recheck everything twice. I ended up needing to update my places of work, home address, and several relative’s addresses. I also decided to remove a number of my foreign contacts since the investigator for my secret clearance told me I didn’t need to list them (I made a note about removing them on the TS eQIP).
I recommend you treat it as though it is entirely new (go through line by line), but you get to save some time where the old values are still correct.