1. Depends how long you will have to live
2. It can be done indefinitely but you need assets rather than cash. This is because you need your principle to grow at least at the rate of inflation so your income grows at least that of the inflation rate. Cash in a bank probably won't do it.
$3m in property or shares would likely get you $50k pa after tax. And as long as you live within this it will increase every year fr the rest of your life.