I own a L3901 purchased new in 2021. Up until this summer regens occured regularly between 15 and 20 hours. 15 in the winter (snow plowing, firewood) 20 in the summer (finish mower and brushhog). So far this summer I have not had a regen light come on. 44 hours since the last one. I have 403 hours on the tractor. Should I be concerned? It starts and runs fine. I am new to Kubota and deisel tractor. My only other tractor was a 1950 8N I had for 34 years.