Here is a tweet from Ross Miner. Doesn't sound like these visits are quick...
Here is an article from a track athlete about doping control. It sounds like they get tested out of competition VERY frequently. Three missed tests equal a positive test- so they have to be diligent about alerting the agency to any schedule changes.Ross Miner@rossminer
Congrats to @simonshnapir on a new personal best time for an out of competition drug test! Less than one hour :-p