Yes you can use a potted fir tree as an indoor tree several years in a row if you remember to water the potted tree all summer and then keep in mind that fir trees can only handle the heat of your home for a few days or else they wake up from winter dormancy. They also suffer from the lack of humidity inside homes. You do not need to repot the tree unless the roots are so packed inside the pot that water runs right through the drainage holes and you see roots trying to poke from the bottom of the container. Place the tree where it would get just morning sun during the summer. After two years as a potted tree I would transplant it into the ground. Good luck and keep growing, Marianne Binetti