I bought Motoul 600 to replace the factory fluid, but now I am reading that it lacks some lubricants and needs to be drained often.... Can somebody please clarify as to how long "often" is.

 

Motul is not bad, it is more susceptible to water absorption (hygroscopic), so you would need to flush it every 6-8 months.

Its dry boiling point is slightly better than ATE Super Blue/Type 200.

Personally, I would go with ATE Type 200 for a street car.

 

I just rebuilt (put new seals in) my calipers after 20K and around a dozen track days. I am on my third set of pads and tires and I have been using Motul before my first track day (2K). The calipers and pistons looked fine, I could have probably waited another 10K/set of pads before doing this. The dust boots were a little deformed from heat and starting to crack a bit but nothing to serious. The O-ring seals looked fine and there was no sign of poor lubrication wear or gauling on the pistons or caliper cylinder walls. An awful lot of people like myself have been using Motul for many years, I cannot say that I have ever had or even know any one that has had problems with it.
Of course I try to bleed the brakes after every track day and my general maintenance schedule is far more advanced compared to a typical streetcar. But this is what you have to do if you track your car, if your not tracking your car then IMO you don't really need high temp brake fluid anyway.
I have probably never gone more than 3-4 months without at least bleeding the brakes, much longer than that and I usually flush it. If it’s strictly a fast running street car any good brake fluid from your auto parts store will due. I have had good luck with the Valvoline high temp fluid from my local store, in a pinch I have even used it for track work.

 

This is true for any high performance brake fluid.