I have noticed in the past month many forum members not only want to solve your oil issues some by erring far from the owners manual from viscosity, and or OCI, many also want to go into psychological, health, and any other issue they can think of, or may be having them self at the time.
I would however choose to follow the time based OCI, it should state this in your owners manual, however it may not hurt to shorten it some if you feel the need to. I don't see a need for a UOA, or any frivolous money spending. What can happen with short trips are a few things, 2 that really stand out are fuel dilution, and condensation. With today's multi-port fuel injection fuel dilution is almost a non issue on 99% of stock engines (I guess some high performance engines may have an issue, but not sure). Condensation from hot/cold or warm/cold may be your biggest problem, by bringing the engine fully to operating temperature, and keeping it there for 30 minutes really gets the condensation, and some of the fuel, and other contaminates out as well. Of course this does not mean idling, it's driving the car that's why many high mileage cars have many more miles left in them, highway miles don't really hurt a car.
As for the walking it's up to you, however you could really save some money by walking to work. I'm not sure if I would dream of living that close to work or not, can't play hooky to work outside in the front yard, garden etc LOL. I'm not trying in any way to say your lazy by not walking, so don't get me wrong please, and I'm betting you may already do some walking, however I could see many many reasons why someone would choose to not walk to work as well.