Avianca's Lifemiles program is relatively unknown as they only joined Star Alliance last year. They sell miles frequently (like in right now in April) for just 1.5 cents per mile.
Now they offer a special perk (that may go away any minute) – Singapore Airlines Business Class is available for miles redemptions. Singapore Airlines usually restricts access to most long-haul business class seats on A380 and 777ER flights for Star Alliance partners.
It's not known why LifeMiles suddenly has access to such inventory but a number of people are reporting success on Ben's blog. All you need is 40% of the required mileage in your account – you can buy the rest on the spot.
I'm still waiting for my miles to post from the Shopping Mall deal last October. In early April Lifemiles sent an email that they will post within 30 days.