The good thing about the Singapore Grand Prix being run in the evening is that there is no rush to get up and head out first thing in the morning. The most urgent thing before lunch is making sure you get to the hotel breakfast before they stop serving.
It also means when you do eventually head out at a reasonable hour you have time to do tourist things before heading into the Grand Prix.
The last time I was in Singapore was just a few months ago, after my 6 weeks in Europe. I had planned to do a few things in Singapore on the way through back to Australia but I ended up spending most of the time in my hotel room after eating a dodgy bread and butter pudding and getting some nasty food poisoning – this trip was much more enjoyable.