On the main sequence, yeah. But white dwarfs -- which are technically stellar remnants -- are indefinitely stable. They just keep cooling. It's surmised that

On the main sequence, yeah. But white dwarfs -- which are technically stellar remnants -- are indefinitely stable. They just keep cooling. It's surmised that they'll still be quite a lot warmer than the universe's background temperature in 10^15 years. This has yet to be observed, but red dwarf stars, when they reach the end of their lifespan, should contract and become white dwarfs. It's said that our sun will also eventually end up as a white dwarf. White dwarfs are superlatively stable, long-lived, and quite hot. And there are already quite a lot of them. If you're going to build a Dyson sphere/swarm, they're a very good choice. Though red dwarfs aren't bad...