31 years old ,hard erction for 10 mins

Hi

Im 31 years old had a good hard erection for about 10 mins while having sex with my gf  in  the  evening.  I had this erection         after  mastrubrating for 4  times in  the morning  and afternoon. I also had just one  meal that day.

Is that a good  enough erection or should I have to have  erection  longer than  that?

Im trying to test my limits and  want some one to rate my libido

Thanks,