Seabound what are you referring to Star Alliance Upgrades or just plain buying promo points from Lifemiles and the booking your itinerary?

If you buy the points, you can book in Economy, Business or First class which means you don't need to upgrade.

But if you are referring to revenue tickets then it is a whole different ball game. Clarify please so that others who may not know can guide you!!

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Upgrades with Miles

In LifeMiles you can redeem your miles for Upgrades to Business Class in all flights operated by Avianca. To enjoy your Upgrades with Miles, you must keep this in mind:

Only valid for Avianca flights.
It may be granted if there is availability in the upgrade Business Class (Class I).
People you choose can also enjoy this benefit, in order to do so, the transaction must be done by the miles’ owner.
It will be available only through Avianca’s Call Center, after the ticket has been issued.
For domestic flights in Colombia and Peru you can get the upgrade in all rates except Promo rate.
For international and transatlantic flights, it can be granted in all commercial rates.
You can also apply for the upgrade in domestic or international flights when redeeming a ticket in the product All Seats
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Star Alliance Upgrade Awards

Now you can enjoy your LifeMiles for upgrades from Economy Class to Business Class or from Business Class to First Class on flights of Star Alliance airlines members. To request an upgrade please consider the following:

Your ticket must be purchased in Y or B classes to upgrades to Business Class, or in C or D classes for upgrades to First Class on any Star Alliance carrier. Some airlines allow upgrades from other classes, find out more information.
You can only request an upgrade for up to 2 flight segments.
Your booking must contain a maximum of 4 passengers.
Codeshare flights upgrades do not apply.
You will receive immediate confirmation if your upgrade was processed successfully or not when making your request.
Request your upgrade on Star Alliance airlines members.