I've read that sometimes you should change your exercises every few months or so to get better results. Should you stop using that exercise and pick a new one or keep doing it and change the grip a little so a different angle of the muscle is hit instead?
give program outline and goals for a more detailed response.
To continue making progress (as opposed to treading water) you probably need to switch something up when progress stops.
There are many ways to switch things up. There should be lots of articles around here to provide ideas.
Just cahnge SOMETHING every foru to six weeks at least be it grip spacing, load/set/reps schemes, the exercise, rest periods, tempo. A new stimulus no matter how slight to keep things fresh and the body adapting.
Personally I change my exercises pretty much from workout to workout, however I stay in the same bracket. For example, I train using a total body 3 times a week. I always do some sort of upper body pushing exercise. Could be Bench, Incline Bench, Close Grip Bench, Military Press, Push Press or any of the above with dumbells. Train the movements, not the exercies. Unless of course you are a powerlifter I guess.