Wings are one of Terraria's most important Hardmode mobility upgrades. They change exploration, arena design and boss movement, so the right pair should be judged by how it fits the rest of the loadout.
Progression stage comes first
Compare wings that are realistically obtainable at your current stage. Planning around a much later option does not help if mobility is the problem now.
Flight time is not everything
Vertical speed, acceleration, handling and the way wings combine with other mobility accessories can matter as much as raw flight duration.
Boss versus exploration use
For boss fights, reliable movement and recovery may matter more than maximum travel distance. For exploration, longer sustained flight can be more convenient.
Accessory-slot tradeoff
Wings consume an accessory slot, so compare the mobility value against what another accessory could provide. As your loadout improves, slot pressure becomes part of build planning.
Upgrade only when it solves a problem
If current wings already handle your boss arenas and exploration needs, a small upgrade may not be worth the farming time. Upgrade when the mobility improvement is meaningful.
Source: Official Terraria Wiki — Wings.