If you are using 24 hour days, you would have about 66 days before you get the first warning (50% of max rad).
50% * 30rad / 0.0000055555rad/s / (6 / 12 * 0.95) = 5,684,267s = 65.8 day
Remember that the half the shielding only (roughly) doubles your lifespan, whereas full shielding increases it 20 folds.
Edit: Also, if at any point your orbit stayed a little too long in the belt it can quickly affect these values, each minute corresponding to over 16 hours of cosmic radiation.