Whats the plan?
Even if it was 3-6 minutes that would probably be an improvement.

my little cock spurts its cum in my pants or in my hands usually. half the time i try to make love to my gf I cum before I can. when I do be able to last long enough I can only last a couple seconds inside her.

That's a tough situation. Like the usual response is, please her in another way, but what about from her perspective, if she wants to do something to you and it's not really possible.

Would you rather have average size or average stamina?

average stamina.

ive asked her is it a problem and she tells me that i shouldnt worry. she knows i cant help it but i can tell it bothers her

No reason to doubt you there, thanks for sharing.
Why worry about size when it can't really be used anyway? It is a serious issue.

Recently I had a conversation with my gf, I brought up that last time we had sex, we had spent about two hours in bed and that my penis was in her for about two minutes the whole time. She asked if I was complaining, I said no just noticing. She said she had a great time, and so did I, so why bother about time, as long as you're both satisfied

I always thought it was because I jerk off too much and wear myself out, but I don't come unless I squeeze the muscles down there. I have to make myself cum or I just go until I go limp ( which gets quicker with my old age). In fact that's my problem, I can barely get hard anymore, I usually stop at about 3/4 of the way and I and don't get fully hard anymore, usually can't even penetrate my wife and we have to do oral.

Oral is very, very nice :)