maybe you find something of interest here:http://www.upmpg.com/tech_articles/motoroil_viscosity/
I don´t think, that you change a oil "too often", but as others pointed out, it may only cost you extra money, for no benefit.
To put perspective on the "too often" claim, in race cars, you would change the oil afte every race/weekend (talking teams with sufficient budgets here), depending on your race series, this can be anything between 300-1000km.
Is the needed? - perhaps not, but then compare to anything elese the 100-200$ for the oil does not make much difference.
The same would go for gearbox oil on most race cars, as the gearbox will get rebuilt after each ace anyway.
So you will be "safe" to change your oil often.
Depending from your driving and your location (Temperature/winter driving/cold startetc.) you may don´t need a 5W or 0W oil for your application.
If you do mainly track driving during the summer/spring then you could go 15-20W.
Keep in mid that most "real" race cars get pre-heated so there is no need for good cold-start lubrication. This is more an issue with daily driven high performance cars and cars like a WRC when they spend the night in parc ferme during the Swedish Rally, and you may need to start your turbo engine at -25°C the next morning.
Too "thin" a oil can cause some problems,wear in your valve train, especially if your car uses some hydraulic lift control &/or wear compensation in the valves.
Here changes in oil viscosity (too high oil temp) can cause variations in valve lift.
But that´s something, your engine guys can tell you more about.