How is the tread currently? If you think it they are adequate for turn in, then get a new set of non-run flats now... and put the run flats back on before you turn it in. You can either sell or reuse the non RFT.
2015 M3 - Mineral White, Sonoma, Exec, LED, Adaptive Suspension, HK, 19" Light Alloy, 6MT ED 7/7/15 - Adrian
2013 535i - Space Grey, Biege, M-SPort, Premium, Tech, Cold Weather, Luxury Seating, PDC, 6MT ED-10/11/2012 - PCD - Greg Poland