Yes, doubling your income and maintaining your lifestyle would make a huge difference. In many cases such an extreme bump isn't reasonably available.

I believe GP was more referring to the rough rule of thumb is to have 25x your annual expenses by the time you retire. +5k income versus -5k expenses, you're better off cutting your expenses. By cutting expenses, the target drops by 25xExpensesCut, and you're throwing an extra ExpensesCut towards savings, helping on both sides of the equation. Going from spending 95% of savings to 90% makes a huge difference on the timeline, but 50% to 45% is much more modest since the timeline for compounding growth is so much shorter.

Using 70k income, 50k expenses, and a 5% return, this would take about 30 years. [0]

75k income, 50k expenses goes to 25.2 years [1]

70k income, 45k expenses goes to 24 years [2]

150k income, 50k expenses goes to 10.6 years [3]

Another detail often forgotten about, salary is stated before taxes, spending is almost always after taxes. That further increases the power of decreasing expenses.

[0] https://networthify.com/calculator/earlyretirement?income=70...

[1] https://networthify.com/calculator/earlyretirement?income=75...

[2] https://networthify.com/calculator/earlyretirement?income=70...

[3] https://networthify.com/calculator/earlyretirement?income=15...*