Your level of training should be such that you can draw, fire and hit your target reactively without thinking about the steps needed. This frees your mind to deal with the threat situation - evaluating the threat, evaluating retreat options and non-violent resolutions, etc.
Once your training is such that you can at least get your firearm quickly into service, you can move on to more advanced training. Such training would include using speedloaders, cover, movement, contact-distance techniques, etc. All that "fun stuff".
I'll add the normal disclaimer here that one should carry a less-than-lethal form of defense (e.g. pepper spray) when practical. Even if for no other reason than to give you a chance to avoid shooting the gene-tampered turkey who's asking to be shot.
The bigger question is can too much training hurt you in court? I think it can. Pax's idea of re-taking the same training course every year (or two) doesn't get you into the trouble. It's the guys who take the ultra-advanced courses or courses in hand-to-hand/knife fighting too. I can see that training being flaunted before a jury to paint someone as willing to skip less-lethal means just so they could shoot someone.
BillCA in CA (Unfortunately)