The Freshwater Master Kit:
Some of the tests need to be allowed to cook longer in cold water but generally you're looking at 5 to 8 minutes on each.
If you didn't mix up the #2 bottle of the Nitrate test really well it can take up to 15 minutes for it to finish reading.
If your Nitrates are rheeeeeally high, like 300 or so, the Nitrite test can take a long time to react. If your Bottle #1 on the Nitrate test turns the test water dark in color then don't bother finishing the test - CHANGE THE WATER NOW!
Often if you've got Prime (etc) in the tank then the ammonia test can take a little longer to cook up.
The benefit of the Master Freshwater is you can reduce the number of drops and the water used for the test if you get a child's medicine dropper with milliliter and ounce markings. Nitrite with 1ml and 1 drop. Nitrate with 2ml and 2 drops each chemical, etc. In my experience if you only have one or two tanks the chemicals will become crusty and old before you use them up. Keep some paper towel on hand to daub the dropper tips off when you're done with each bottle to keep the chemicals from coating the outsides of the bottles and keep the whole kit stored someplace cool but not refrigerated.
Since I use a dropper to take water from the tank for the tests I went ahead and got some nice high borosilicate Erlinmeyer 10ml flasks. Cost about $28.00 for 12 of them but they rinse very clean, stand up on their own and you can swirl them to do the mixing instead of shaking and having the chemical reaction squirt chemicals out on your hands. Since they're conical they'll roll in a circle and you get a nice visual depth through them from side to side. Haven't broken one yet in two years.