Do emax porcelain veneers drop half a shade after a couple of weeks like my dentist says it will?

Worried the colour we chose is too white/fake looking. Wanted natural looking teeth and decided to go one shade up (A1 or B1 HT) from my natural teeth for my temps - I thought they were perfect but dentist recommended 1 shade up. After 1 day the temps looked too yellow so I agreed with my dentist's suggestion (BL4-HT). Now my final veneers are on and I'm panicking. Will the cement stabilise over 48 hours and will the colour drop by half a shade like he says it will?