Too much of spare cash

I have been investing very heavily like 90% of my networth since young, started to cut back as getting old but still hold like 70% into various products (stocks in US/SGX/KLSE/HKSE take up 75%, various funds/bonds 25%).

I am still working and making very good money. When I trimmed my portfolio down by 20%, I am already having problem with to do with the extra cash, I have to liquidate more especially US stocks since I don't wish to have estate duty after I pass in. Only thing I can think off is to get another property but quite unlikely as my son is not keen to take over.

I know this is a good problem to have for most people, seriously wanting to find out what other options that some of you have done. RM won't help as they only want to sell products.