The only time I would say you definitely shouldn't return early is if you can't easily see every return within a single screen (whatever the standard might be for people working on the same code base), you should at the very least be adding comments indicating that the function can return early if there is an early return.
The only time I would say you definitely should return early is if your code looks like...
boolean valid = true;
if( condition1 ) {
valid = false;
}
if( valid ) {
...
if( condition2 ) {
valid = false;
}
}
if( valid ) {
...
if( condition3 ) {
valid = false;
}
}
... (etc)
If you find yourself in either of these situations, however... you should probably be refactoring the function.
