Your father's satellite is very high (1400km, 1000km above the ISS) at the edge of what is classified as low earth orbit. It will be up there for a long while but the chance of it ever hitting anything is infinitesimal.
It is worthy of note from https://spacenews.com/upper-stages-top-list-of-most-dangerou... that in a list of the 50 most concerning objects in orbit, 78% are rocket bodies, and 80% were launched before 2000 when various mitigation strategies for space junk began to be improved.
There is therefore a Pareto principle at work here. We are tracking over 25,000 objects, but only a few of them contribute most of the risk, and we aren't adding as much to the risk as the number of launches would make you think.
Edit: I just looked up the formula for orbital period and it turns out period is proportional to radius^(3/2) (See: https://en.m.wikipedia.org/wiki/Orbital_period)
It's only about 50% larger (1+1400/6371)^2 = 1.49
Almost everything we do carries a small but non-zero risk of something which, if you stretched it over a hundred thousand years, would almost certainly be realized.
On the other hand, the average damage from a collision in space within 100,000 years is also pretty small.
Of course, I am assuming a few things, like their orbits don't decay, they aren't exactly synchronized (i.e. they drift, and will eventually cross every point on the other's), but also that the uneven gravity of Earth doesn't corral them into narrower orbital paths (which it absolutely will, increasing the chances of collision).
That's for only two satellites. There are literally thousands. And when they smash apart, they can each generate hundreds more killer-sized fragments.
Kessler syndrome is a very real possibility on a long timescale.
We should be more careful the junk we put in space.