https://res.inlandsbanan.se/ Goes from Kristinehamn to Gällivare (1300 km), via Mora, Östersund and Jokkmokk. Mora to Gällivare is about 15 hours, including lunch and fika stops along the way.
With the inlandsbanankort, you can use the train as many times as you want during a 2 week period.