The beauty of torrents is that as soon as someone else starts to download, provided they're a good swarm member, the overall seeder capacity increases.

You don't need to have 100% of the data to start seeding, you only need a single chunk.

It might take several weeks for that first peer to hit 100% but it should be quickly followed by a whole lot more as those peers are all seeding each other up to 99% amid the process.