Honestly, vitamin d daily dosage was a one of topics on this forum that we could not reach consensus as everyone had different opinion. Even the scientist cant agree on this one.
My take is that based on estimated daily reqirement of vit d is somewhere between 400-800 IU, so I beleive that 1000 IU should be more than enough, though in some circumstances (deficiency) it could be upped to 2000 or in rare cases 3000 IU, and than reduced.
But, thats my opinion. Also some sources say that max uptake for vit d is 4000 IU but that is debatable.
And last- too much vit d can cause sleep issues and even mild insomnia.
In the end, we all all different.