(and this all is based on an if)
If we could live an infinite amount of years, yes we could discover an infinite amount of planets. but physical limitations disable us from ever reaching infinity, such as our universe ending, our solar system ending, our world ending, us physically dying. all which work. but what is to say the dwarf planet pluto, is non-existent...i mean, no body has ever physically set foot on pluto, but to say it is not real is stupid...obviously pluto is real...that being said, just because infinity has not been reached that does not prove it isnt there...obviously infinity is a term to represent all possible numbers, but physical limitations stop us from doing mental realities