I am currently working on a bathroom remodel project that involves running new copper supply lines to the faucet and toilet. I have completed a number of remodel projects that involve plumbing skills including a kitchen remodel and moving the location of the hot water heater. I am confident with my ability to sweat fittings with the exception of ball valves. I fear that I am going to damage the valve by overheating. I am currently using a BernzOmatic TS4000 and MAPP gas. I am thinking about using threaded ball vales instead of the sweat type. Any advice?
Thanks much

Just make sure the valves are in the open position. And if your not 100% sure, wrap it with a wet washcloth or keep one nearby. Good choice over threaded, as that makes them easier to position.

The only other thing I would suggest, as a precaution for the valves, is to use propane instead of mapp. Mapp burns hotter than propane, and mapp is generally used for larger size pipe/fittings. Propane is more than sufficient for the 1/2" pipe. If you use mapp, apply the heat sparingly as the smaller pipe heats up a lot faster than with propane. As stated, keep the valve open and hang a wet rag on it to absorb heat. The valves are more durable than they appear, & I have never ruined one while soldering, with or with out using a wet rag.