Caveat: I'm neither a welder nor a metallurgist...But my understanding is that Ti is intolerant of poor technique. If the welding is not done properly, it can and will fail. But if it is done properly, it should be fine.

Steel, by comparison, is easier to work with.

To the OP: consider that, for the price of a good Ti frame, you can almost buy two good steel frames. Then you'll still have a lifetime of bikes.