My understanding is that premium is only paid when you join CPF life. That is, anytime from 65-70.I think if you passed on before CPF Life started payout. Your CPF nominee only get back whatever money you put into RA without the interests gained from age 55 to 65(or whatever age u intend to start CPF Life payout).
So what I understand that to mean is that, before joining CPF life, the amount in your RA earning interest belongs to you. If you die before joining CPF life, all of your RA goes to your nominee.
When you join CPF life, 100% of your RA goes to paying the premium (10-20% if Basic Plan). At that point, any interest earned by your premium goes to the pool.
So if you contribute $300k at age 70, that's your premium. And if you die at 75, they will calculate your payout (say 20k/yr, so 100k over 5 years), and then your nominee will get your premium, less payout. (300k-100k=200k)
So there is a loss of interest in that sense.
Having said that, if you took the Basic Plan, and say 20% of your 300k goes to the premium, you will have 60k in CPF life pool, and 240k in your RA. However, your payouts are taken from your RA first.