Hi everyone I need opinions? But please don't be to harsh :) thanks?

So I am exclusivly breastfeeding my daughter who is 7 weeks ( i am very very proud of myself) I didn't stick it out with my first child gave up easy and was not educated. My first child was also c-section and I had my gallbladder removed (emergency 5 days after she was born). So all in all my first expeience in giving birth and breastfeeding went out the door! So here I am 7 weeks post partum breastfeeding (it was rough but I stuck it out) and I had a succsseful VBAC drug free. So I am training for a marathon in 6 months and I would like to stop breastfeeding before I do the marathon...But I would like her still to get breastmilk so my question is....Do you think its alright if I feed her and between feeding during the day I pump and stock up on breastmilk so she can have it for another couple months?? What is your opinions on this? I also would like the xtra breatsmilk for her food.... I plan on using a baby bullet to process fresh veggies and fruit. She will be 8 months by the time I run the marathon. Will doing this mess up my supply? Or make me more engorged at night seeing how she sleeps almost through the night she can go 7 hours sometimes. If you have any suggestions or advice please help :) thanks!