You would need round 1400 "perfect" trades going from diamond > coffee > gold > coffee and repeat (d>c>g>c is 4 trades and takes 1 hour) or 360 hours if everything lines up perfect to get to 1e300 needed to level all 11 girls to 56750.
In reality it took me 45-50 days and I think 1500-1600 trades
Your store multiplier have very little to do with how fast you can do it. My combined earnings/s at 56750 was 1e144 and that is nothing compared to 1e300 needed.