I have used it once in a while, specially when I'm not in he mood to work out, I might continue using it , what are the negative effects on using ammonia in the long run?
I am not sure of the actual health consequences but there are much more effective ways to be ready to train. The first 2 things would be to be properly hydrated and have a good meal 90 minutes before training. That will have your body fueled with the right nutrients to train. If you were really tired you could try adding a cup of black coffee or just a pure caffeine pill. I wouldn't use the caffeine every day but on those days you are really struggling it may help.
It isn't great for your nasal passage and sinuses but there will be no long term health consequences if you only do it occasionally.
I wouldn't recommend doing it more then once per week though. You could actually permanently damage your nasal cavity and loose your sense of smell if you do it too frequently.