There are currently 329,993 addresses in the Bitcoin network. Say that this number of addresses are created every day for the next 140 years. That's 16,862,642,300 addresses.
The chance that at least two of those addresses collided is about 9.7x10-29
, using the formula here
I get that the chance is very, very, very small. But unless there is no chance at all there is still a chance. All I am saying is that there should be a check to make sure that a new address does not exist already.
That number should be enough for you.
That number is smaller than the chance of you getting hit by lightning, your wife/SO stealing all your physical money, your bank account being hacked/robbed, your insurance being canceled, and then your home and car being destroyed... all in the same day.
Nothing has a zero percent chance of happening. Very small numbers can and do suffice.