I have a Svea 123R that I used for years without a failure. I had to replace the seal around the valve once, as it began to leak.

Two cautions: If overheated, the relief valve in the cap opens to prevent an explosion. When it does, the vapor that's released ignites, and a very long jet of flame shoots out. As a precaution, I always made sure it was facing away from me. It never happened to me, but it has happened. Use the same caution regarding external windscreens as you would with a cannister stove. Also, inspect (and replace if necessary) the gasket in the cap regularly. Some Sveas have a slightly sharp edge on the end of the threaded filler spout that cuts into the gasket.

Also, be sure to remove the valve key while you're cooking. Otherwise, it gets very hot and will burn your fingers when you try to turn the stove off or adjust the flame.

Mine wouldn't really simmer, but you can adjust the flame fairly low.