0.03 BTC sounds very high even for a 10 BTC budget.
It may be just me, but I have an even lower percentage withdrawal rate, somewhere between 1-2% a year.
The rule is originally intended for people who are retiring, so that the money could last about 30 years. If you haven't reached at least 60 maybe that's why it seems high to you.
Although I personally don't think the same. Bitcoin will continue to grow above inflation, well above it for many years, so with 4% or less you will not only not run out of money, you will continue to gain purchasing power.