I have had an Amex Platinum card for over 5 years as well the Amex Black BA Card (Premier Plus). I use the BA card for all my AMEX spending (>£5k/mth) as it earns miles at the best rate. I hardly use my Platinum card and this is why I have not been offered Centurion.

As I travel a bit (and will be doing so more often) I am keen to get the Centurion (travel/insurance benefits etc.). I understand that qualification is based primarily on Platinum spend history.

I have almost a million BA miles so I'm not fussed about collecting at a mega rate right now.

Is it a good idea to switch my spending to the Platinum card? Will this 'guarantee' my invitation to Centurion? How long will I have to wait for the invite?