How is even 45 days acceptable? :0
From an accounting perspective it's convenient to have longer net terms. (At least my accountant tells me that).
MS is using a standard NET 45 on small indies. Which isn't great for a small company that can live and die on a single payment owed.
I can tell you, as a small business owner, (non gaming) all the big companies I do work for have NET 30 or 45 sometimes even NET 60 terms and it hurts.
MS really should have some provision in policy for small developers though. Looks bad from PR perspective.