A limited number of rooms may be available and additional restrictions and blackout dates may apply.

The line above was copied from the T&Cs of the Mastercard promo. The T&Cs are different to normal award bookings.

I think the problem is that the St Regis Singapore is a very popular choice for redemptions so perhaps they put a limit on the number of rooms for this promo. I can imagine a lot of people with a free night thinking "lets stay at a St Regis", I've done it in the past and it seemed to be very popular during the Q2 free nights promo. It is not a huge hotel and maybe it is being loved to death.

This hotel seems to get a lot of negatives here over free nights and upgrades. I've stayed there several times now, only once with a suite upgrade but they did give free breakfast and internet, something they were not required to do under the T&Cs. IMO they try hard to deliver to SPG members.

Hopefully they will continue to participate in upcoming promos and anyone wanting to redeem will need to remember to book well in advance. In short, I like this hotel and I think it gets blasted more than it should.