Is Investing your surplus savings (salary - expenses) important?

I believe it is absolutely important and it can add 12 extra years after your retirement. Let's understand how...

I will try to explain the importance of investing with 2 cases:

Case 1: If you don't invest your surplus savings (salary - expenses) and keep them in a savings account.

Case 2: If you invest your surplus savings (salary - expenses) and keep them, let's suppose in mutual fund scheme(s)

Assumptions:

1. Age: 30

2. Retirement Age: 60

3. Post Tax Salary per month: 50000

4. Expenses per month: 30000

5. Salary increment yearly: 10%

6. Expense Growth per year: 5%

7. Inflation: 5.5%

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Case 1: If you don't invest your surplus savings (salary - expenses) and keep them in a savings account with an interest rate of 3% (moderated to 1% after 30 years)

Your money will grow to 36,797,140 or 3.7 Cr when you will be at the age of 60

After your retirement, you can use 3.7 Cr for only 3.5 years to maintain your expenses in terms of your lifestyle

So: Do not invest -> get 3.7 Cr @60 -> will last for only 3.5 years after retirement

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Case 2: If you invest your surplus savings (salary - expenses) and keep them in a mutual fund scheme(s) with an investment rate of 15%

Your money will grow to 237,908,750 or 23.8 Cr when you will be at the age of 60

After your retirement, you can use 23.8 Cr for 15 more years to maintain your expenses in terms of your lifestyle

So: Invest -> get 23.8 Cr @60 -> will last for 15 more years after retirement