How Much Do You Warm Up Before A Meet?

I ask this because I did a 500 and then 5x50s warm up for a meet this past weekend. When I swam the 500, I was cruising but was literally dead after about 6 laps. I go much faster in practice sets when we do distance and it was frustrating to say the least. I recall that I did a 1,500 warmup in my youth and had a good meet. I also know that in workout I am usually at my strongest after we do about 1,500-2,000. So, I am tired of being a workout warrior. Does 1,500 of warm up sound crazy? Thanks, Rob