If I don't withdraw all the money from my SASSA grant, will the remainder be lost?

The long answer

No, the money will not disappear, but SASSA says you need to withdraw some of the grant money within 90 days (3 months), or your account will be suspended and might then be deactivated (closed) by SASSA.

SASSA says that legally, there is no limit on how long your grant money can stay on your SASSA card, as long as you withdraw some money regularly. Even a small withdrawal shows that you are still using your account. 

SASSA actually recommends that you don’t withdraw all your money at once, because of the risk of being robbed while carrying a large amount of cash. But if you go longer than 90 days without drawing any money, SASSA will suspend the account.

Wishing you the best,
Athalie