Yes, Tournament outfits last forever but the way to get them changed as tournaments don't exist anymore. Furthermore, if you do not purchase the outfits with Tournament coins they won't be account based (apply to all your characters), only character based.
More details here:
Tournament Coins will expire on March 21, 2023, server save.
Please note, all Tournament Coins will also be removed from the game on this date. So make sure that any remaining Tournament Coins are used up before March 21. Any Tournament Coins that have not been used by then will disappear.
With some exceptions, rewards that were available for Tournament Coins in the Store will become purchasable for Tibia Coins after Tournament Coins have ceased to exist.
About the exceptions:
· The lion of war outfit, the ogre rowdy doll, the retching horror doll, the sublime tournament accolade and the tournament accolade will be available from NPCs for Drome Points.
· In addition, NPC Walter Jaeger offers the tournament items cerberus champion puppy, demon doll and vexclaw doll for Hunting Task Points.
· The dragon slayer outfit will be obtainable at a later time. We aim to implement a challenging way to earn it ingame. An exact date for the implementation has not yet been set.
Outfits and mounts bought for Tibia Coins, Drome Points or Hunting Task Points will only be usable by the purchasing character, they will not be unlocked account-wide for all characters like their Tournament versions.
Source: https://www.tibia.com/news/?subtopic=newsarchive&id=7200&fbegind=23&fbeginm=1&fbeginy=2023&fendd=22&fendm=2&fendy=2023&flist=11111111