TR is super conservative on coasting, its not realistic for where I ride. But if you live in mountains it could be realistic.
For example here is a recent 3 hour ride on flat roads:
coasting was just 2 minutes and 19 seconds (1.2%) of total duration. I spent about an hour riding within the city, so I had to do stuff like:
and make right turns and small loops / detours if I saw traffic was going to stop me.
You need to adjust total time as necessary based on your roads. Adding only 5-10 minutes to a 3 hours ride is normal for me, but not for everyone.