Is there a maximum delay limit for window.setInterval
According to the setTimeout documentation on the public wiki MDN there is indeed a maximum, though it doesn't seem "official" - the limitation is a signed 32 bit integer.
Maximum delay value
Browsers including Internet Explorer, Chrome, Safari, and Firefox store the delay as a 32-bit signed integer internally. This causes an integer overflow when using delays larger than 2147483647, resulting in the timeout being executed immediately.
The value of 2592000000 is indeed larger than 2147483647 thus causing the overflow.