Some of my best races were after a long warm up. Warm up is the key wording here.
There is no set mileage for proper warm up for an individual.
In the beginning fo my racing I would never warm up, for fear I wouldn't be able to finish the race due to using up all of my energy (silly thinking now).
Over time, I figured out that the warm up does what it is suppose to do given
the chance, to warm up.
Doing so before prepares you body to head off and race a 10 miler with an opener sub five minute first mile. Continue on to back it up with a second mile without blowing up the rest of the race.
After all it's all about you, doing your best in a competition. Who cares if it takes ten minutes to warm up ( that alone tells me the person is a rookie and filled with uncontained adrenaline. Too nervous to warm up properly).
I would wear layers of clothing to warm up my muscles. When I stood on the starting line, I had a sweat, a light one going. I would be ready. My heart would be able to handle the burst of the blasting the first mile or so off the starting line.