According to standard firecalc, assuming default values of 75% stock weighting and 0.18% investment expense ratio, a 4% withdrawal rate would last 30 years about 94% of the time. Bumping your withdrawal rate up to 5% occasionally would make the success rate drop. How much it would drop would depend on the timing and frequency of the 5% withdrawals.
The previous paragraph assumes, though, that you're talking about taking 4% of your $1.5M the first year, then increasing that withdrawal amount by inflation for subsequent years. If you're talking about taking 4% or 5% of your portfolio value every year, then you will never go broke but your annual budget will vary wildly and may get very small (like 4 or 5 cents if your portfolio drops in value to $1.00).
"At times the world can seem an unfriendly and sinister place, but believe us when we say there is much more good in it than bad. All you have to do is look hard enough, and what might seem to be a series of unfortunate events, may in fact be the first steps of a journey." Violet Baudelaire.