For the top level racers at TdF the standard warmup for a time trial is one hundred kilometers. Slower guys do 60 or 80.
Then we get older and it takes even longer to warm up.
One of the best rides out of a whole lifetime was with a friend in his early 60s who came out for a 120 mile jaunt and purely sat on the back for first ninety miles. Then he came alive. He worked the front of the paceline and forced us all to hammer along at 28mph. He said it was the first time in years he had been properly warmed up. Then he bought the beer and was the only one with enough energy left to enjoy it.
All the club rides in the 60s and 70s automatically started with a ten mile warmup. Might take 30 minutes, might take 40. Many thought that was was too short.