Why? For example (not necessarily the best example, but a valid example) you can still get 2.5% from Singlife on the first $10,000. That means you’re guaranteed to make money as long as that deal lasts while your 1.X% interest mortgage chugs along at standard pace. 2.5% definitely beats 1.X%. Even CPF OA is offering 2.5%. There’s also the fact mortgage payments count toward DBS Multiplier account interest, so if you’re nearer to having no mortgage payments you’re also nearer to possibly reducing interest earned on your savings. And you reduce liquidity, too. All not fabulous.
The second best idea you have is to accelerate repayment on a 1.X% mortgage? I suppose mortgage borrowers should thank you for doing your part to keep mortgage interest rates in Singapore ridiculously low, but you’re not required to do that.