yeah AWS tends to have capacity issues during high volume periods like black Friday (I think this is now actually because most large users pre reserve a buffer pool of vms sitting unused) -- but I have never had an issue where AWS has told me there would be no capacity for months. Its usually swapping AZ or regions or being slightly flexible on your sku. And if you are sensitive to this and find it happening take a look at your sku loadout you may be choosing a very high demand vm type and shifting just slightly gets way more capacity.

^^ and by capacity I am talking like 10's or 100s of vms being available not 1.