As one, who has sold and serviced Dish Network since the days of the Dish300 with a single legacy lnb, I'll have to say that there are some versions and makes of Dish lnb's that have high heat tolerance and others that have failed in large numbers.
The most durable configuration is basically the Dish300 with either the legacy single or dual lnb.
The most durable Dish500 configurations are the legacy lnb's with SW21's and the original legacy twin that was Made in Japan, The sw21 is vulnerable, however, if the connections were exposed to the weather. So, they must be weather protected. The Made in Japan legacy twin has both of its ports close and near the center. Less durable is the CalAmp Made in USA legacy twin identified with two outboard ports. The most durable three satellite configuration is the Japanese legacy twin with cascaded sw21's, when the sw21's connections are protected from the weather. The Made in Taiwan heavy DishPro plus twin has been very reliable.
The SW64 and the DP34 has been problematic at times. The CalAmp Made in USA legacy quad often experiences heat related problems.
The lnb's most vulnerable to heat damage are the DishPro twin Made in China bearing date code CSS9601. Dish is still paying to reimburse dealers to replace those. Any of the SuperDish lnb systems are very heat vulnerable. The lightweight DishPro plus twin made in USA by CalAmp has a high failure rate. They are failing so bad that Dish is withholding them from current installations.
Too bad customers cannot choose from this list. Local dealers may be a better choice, if you want the most durable and trouble free configuration.
Generally, a lot of electronic components densly packed with lighweight minimal heat sinks are the root of the problem. Evidently, the heavyweight Made in Taiwan DishPro plus twin has a massive heat sink with large cooling fins.