I've found the trip computors oil level warning device handy, seems to operate when the oil level is in the bottom third of the site glass.
My GSA did'nt burn any oil untill around 1000mls and I have used 3/4 ltr since then
5000mls
The consumption is similar to the other two 1200's i've had, i'm sure it burns a bit of oil from the start, but with gentle use (running in) and a 600 service to top it all up again, the oil consumption is hidden until around 1000mls.
My first 1200 stopped burning oil at 12,000mls the second was heading in a similar direction before i p/ex'd it at 10,000 ish
Shep