SQ KrisFlyer Miles Business Class Upgrade Availability
I have a Capital One Venture X credit card and have more than enough miles to upgrade SQ Premium Economy Standard to Business. This is the first time I have ever used miles to upgrade of buy fares with an airline. Naively, I thought I could simply buy the Premium Economy tickets (yes, the one that is eligible for upgrade) and then ask for the upgrade with my miles.
Disappointingly, I was told there is no availability in business class for my route SIN - SFO even though there are plenty of seats available when checking SQ website. I understand that they want to maximize revenue and may release some spaces later on for upgrades/miles when there are unsold seats. Since I am a newbie here, what are the typical release time before departure date (if ever) for me to check to see if I can get to upgrade? Or is it a losing proposition that once they say no availability that means that it will never be available? Thanks in advance.