Well, the blemish is also on the hood and truck, but it is the most visible on the roof. In the sun it just about all disappears but under the unforgiveness of florescent, it shows up like the pictures above.
I will typically wash the car every 2-4 weeks depending on how soiled it gets. During the summer months I wash it by hand with Simple Green and water. In the winter time, 6-8 months out of the year, I will use automatic car washes. Frequency depends on how cold it gets. I have gone 4 months without a wash because of the weather although I try to wash at least monthly in those conditions.
I will wax it typically once in the spring and once in the fall. I have used various waxes over the years.
During the day, the car sits out in the sun, all day long. At home it goes in the garage (with exception to that 9 month period where I lost my garage to "stuff"). Winter months here are dreadful and are overcast for much of the season. I suppose UV damage can still occur but direct sunlight is limited during this season.
I can not see any of this same blemish on the side panels. I didn't get a chance to try a rubbing compound last night but still have plans to try some at some point.
Not that I'm caring for it correctly, but my wife often says, "it's just a car" as I go out to clean it. I'm not completely anal, but for a 5 year old car I think it looks pretty good.