Should I run?

One of the most common maxims you will hear for self-defense is to run away. In almost every context, including against an attacker with a firearm.

Does that make sense? In some cases, I think it does. If I were assaulted by a single attacker and somehow survived it, then I would want to get away unless I was sure there is no danger.
The question that we must ask is, "Can I get out of danger by running?", or "Will I be successful?"
Factors involved in the decision:

• Will I be run down? In other words, am I faster than the fastest of my attackers? Even if not, can I get somewhere safe fast enough, as in behind a door, into a public place, or just a barrier before I can be hit? How do you know if you are faster than someone? I am about forty pounds overweight right now.
• In many cases of mob violence, it may be better to turn and fight, moving laterally to keep most of your opponents in front of you than to turn your back and try to run. If you trip and fall, are taken down, or don't know the area, you could be killed by a group if they overtake you and you are down.
• Does the attacker have a weapon or object he can throw at me? If I can see a stool, bottle, or brick coming at me I have some chance of getting out of the trajectory. With my back turned, it's all dependent on the aim of the person throwning the object.
• I know I can fight well for about three or four rounds. After that, my skills diminish to the point where I could be beaten by a more in-shape adversary. I'd rather try take my chances while fresh, in that case. My point here is that, if I sprint away, and get caught, I have just handicapped my chances of fighting back.
• Can I get to help or a weapon that will even the odds? I may be able to get to my car and lock the door, into a business where an attack will draw a bystander or police/security help, or I may see something I can use to protect myself, such as a baseball bat, chair, restaurant tray, kitchen knife, gun, etc.
• If I don't know if a bad guy has a weapon, I am a good sprinter, but I better grow those eyes on the back of my head quick. If I was being shot at, I'd better run in an irregular, or zig-zagging pattern until I can get to cover [if anyone knows more about this, please write].

I'm pretty confident in my skills in a fair fight, but it ain't always so.