Hi BobbySports
There might be some more sports injury oriented physios out there than me that may give you some sound advice.
My understanding is that the problem with time dosage is "how long is a piece of string". things to consider are:
* Up to 20 mins is the safe range. over that time increases the risk of ice burns to the skin and nerves. I don't know for sure but I can't imagine doing less that 10 minutes is going to affect much. You are right that prolonged cooling promotes vasodilation but up to 20 minutes should be ok.
* How superficial is the injury - deeper injuries will need longer time
* What is the nature of the tissue (or the tissues between the ice and the injured tissue) you are attempting to cool - muscle conducts heat (therefore cooling will occur quicker) vs fat which is an insulator - therefore you will need to apply more to get the target tissue below. tendon and ligament might be something in between.
* Why are you icing the area: decrease bleeding, or reduce oedema etc.
* What method of application is used eg. immersion bath in icy water is more dramatic than application of ice chips in a damp towel etc
* What do you combine it with eg RICE or Ice+ exercise - again depends what you are trying to achieve.
I have attached a systematic review which is rather a lot to wade through. However in the results and discussion you may find some useful points to consider when applying ice. Whatever we do - intelligent thought about why we are doing it and what are we trying to achieve is warranted.
Hope this is of help