Heater not getting hot and it takes a longer time than expected to get hot

Hi, this car has always done this my dad bought it new. Yes, it was outside but no trees around. The pollen filter was old but clean and is now new.
When I took the car I put in a thermostat from Honda with housing. Due to what I thought was lack of heat. I have had four surgeries, so troubleshooting has been slow. I noticed today the lower hose where the thermostat is, and it was cold. Or at least warm compared to the top. Approximately 5-7 miles ride temperature gauge in the middle and not overheating. Heat was lukewarm If I turn the car off for 2-5 minutes IE run into a store. I start the car and the heat is hot. Same as before the thermostat was changed. Only because it gets hot I ruled out the heater core, also the hose is equal temperature.
I worked on cars for many years and found cars with thermostat in lower hose takes forever to circulate. Subaru comes to mind. I have no air in system 100% sure. Or is it possible the wind when I drive is cooling the housing?
Am I missing something? Is this a common problem?
Although two different cars my 2002 Civic blows my Accord heat away. Any help or direction to turn is appreciated. Neil