Turning off invulnerability sooner rather than later will ultimately help you. When you fly to stay alive you will avoid getting into bad habits. An example being sitting on the direct six of a bomber because you're focused on the kill not staying alive. When you lose a pilot you've put time into because you do something daft, you won't do it again! Looking after yourself becomes even more part of the experience when flying Axis.

Also, being more cautious will let kills when they do come build up at a more realistic and satisfying rate.