TimeQuest and Fitter using SDC File

If you're used to Synopsys, I seem to remember doing a lot of save_db and load_db(or whatever the syntax is), so you could do stuff and save your work on the fly. This was more with the synthesis tools rather than Primetime, although I wouldn't be surprised if PrimeTime works the same way. So I'm wondering if your question is, once I've done create_timing_netlist, why can't I just save it off and load it back later. Hopefully the create_timing_netlist doesn't take too long, and once in a script, is a small time of your compile(I am doing some HC240, so I know it's not too small). I have another user doing an EP2S180 with a hugely complicated .sdc, and wanted to save it off after update_timing_netlist, which might be coming. (I don't know for sure, or when.)