"A couple of minutes" is quite a good amount for many dog girls.
Even more if you're stimulating her beforehand to one or two orgasms - orally, by fingering or comparable.
Too much is not necessarily advantageous as she can as well get oversensitive and exhausted. It's a living being and no machine.
If you don't want any noticeable stimulation at all and the ability to basically copulate as long as your muscles are up to the task, then use penis sleeves with small(!) studs or ripples on them together with water based lubricant, not abstrusely long or large ones. Relatively thin and around 10 - 12 cm long ones are enough (if they fit you). They have a dozen times higher wall thickness than condoms and reduce your own
mechanical stimulation to "almost zero". Not your
emotional one, tho. If that's the problem, then no sleeve helps.
Those sleeves can, if selected wisely, stimulate the tissue more intense than a phallus itself (due to the rippled or studded surface). Edit: Ah, by the way.. they're reusable and need to be well cleaned, it's basically a toy, not an one-use-concept.
But then it's probably impossible for you to reach climax, as such I recommend to remove the sleeve if your girl (almost) reached orgasm or is satisfied and finish it raw. As such you can as well get direct feedback & climax and she'll not be left unsatisfied. Remember that there are quite a lot of dog girls which don't really enjoy "half an hour of fucking", as such listen to the signals she sends, that's the most important.
I don't know many people with a phallus which are actually enjoying this. But if he does, then sure..