The problem isn't that the time-window is bigger, it's that even if you crashed within the 5sec
window in ext3, you are almost guaranteed to end up with the old version of the file.
If you crashed within a 60sec window in (pre-fix) ext4, you were almost guaranteed to end up with
a 0-byte file. That's a rather stark difference.
Of course there's no absolute guarantees...if your kernel is crashing particularly hard, the filesystem
driver could go berserk and write 99 red balloons all over the disk. Nothing in the design of the FS
could prevent that...but that's *extraordinarily* rare.