Advice is the...yeah, I probably had that coming, didn't I?
It's too much. If you buy and hold and rebalance every year or so, that won't even take you half an hour a month. There are more important things in this world than money.
Firstly, what's a "10-year all-time high"? Is it different from a 10-year high, or an all-time high?
And secondly, we're talking about Singapore here. The STI's nowhere near its all-time highs, or even its 10-year highs.
US stock markets are at their all-time highs, sure, but that doesn't mean it's time to sell: if you think a new secular bull market started earlier this year when the SPX broke through its double top in the 1500s, it's probably going to go straight upward for the next decade or so. The S&P 500 bottomed out around 60 in 1974, then over the next 25 years it went up in a straight line by about two thousand percent.
In the worst-case scenario, if you'd invested the day before the crash of 1987, you'd still have made about four hundred percent over the next decade and a half.
Here's a thing that everyone seems to have forgotten after the shenanigans of 2000, and 2008, and 2011, and 2013 (in emerging markets anyway): markets generally go up. Sure, it's better to invest at 10-year lows than at all-time highs, but it's not a bad idea to buy at all-time highs unless valuations are epically stretched - and they're really not.
Then give some better advice. We're all here to learn from each other.