Is weight training to muscle failure a good idea? It depends.
With smaller muscle groups, we all commonly train to failure, or close to it, but more often just to the point of excess pain. I'm thinking of examples like curls, forearm exercises, pushups, pullups, cable pull downs and push downs, rows. In fact, many gym machines (which I rarely use) isolate smaller muscle groups in ways that lend themselves to high-rep muscle endurance work (ie 15-20 reps).
With the powerlifts, we do not recommend lifting to failure very often. Just occasionally, to beat the heck out of yourself, and with a spotter. Rule of thumb with powerlifts is mostly to do the number of reps you can manage to accomplish 4-8 times in a row. If you can, for example, deadlift a weight 12 times, raise the weight right away to get down to 6-8 reps for each set.
You Need to Know About Muscle Failure