Several years ago, Briggs & Stratton's came up with the idea of "No Oil Change, Just Check & Add" on their EXi consumer engines. The concept being that due to an improved air filter design, and reduced engine temps, the owner never needs to change the oil, only checking and topping up as needed.
Just Check and Add Never Change The Mower Oil | Briggs & Stratton
But please,
change the oil! This video shows why...................
The temperature thing is a long shot. Due to the move from a side-valve to an OHV design, this takes the exhaust port and valve out of the block and into a separate cylinder head, which in theory reduces the running temp of the block, and therefore reduced oil consumption and oil temperatures. The change from an oiled foam filter to a pleated paper filter apparently prevents and reduces the possibility of the engine ingesting dust, which in turn helps keep the oil cleaner and reduces wear.
Seeing the thick, gloopy black oil dripping out of those engines should be all the visual evidence you need to ignore Briggs & Stratton's advice and take the 5 minutes to change your oil.
I also don't really like the 30-weight oil they like to put in these things. That oil is a very basic mineral oil and is designed to be consistently thick so that it doesn't burn too much due to varying tolerances. This is for a couple of reasons, firstly emissions, secondly for cost control and thirdly for reduced warranty claims due to consumers never checking their oil.
The fact Briggs & Stratton also sell a 10W/30 oil says it all. But you will struggle find that stuff outside of an online store or mower shop.
I went one better with Penrite Semi-Synthetic 10W/30 Small Engine. It doesn't burn any faster than the glue-like SAE30 stuff and its cheap enough.
So, change your oil....................unless you want to shorten the life of your mower.