As others have posted, the aim of the game is to keep as much heat from the Sun out of the satellite as possible. That source is will dominate over any internal generation so if you can handle it, you can generally deal with the rest.
Unless the orbit is highly eccentric, the time in shadow will likely be less than 50% of the orbital period. That combined with the fact that you're relying on radiation to dump heat to space tends to limit the low end of the temperature swing. Your electronics is still going to need a massive working range, but thankfully not down to as low as single digit Kelvin. The more circular the orbit, and the higher it is will further reduce the average time in full shadow.
Of course, when you have a highly eccentric orbit (eg, Moon transfer, planetary transfer), its possible to have very long periods in full sunlight (days, months or years). Eg The Apollo missions spent their entire transfers to the Moon and back in unobstructed daylight. To prevent damage to the spacecraft they had them revolving about once every 3-4 minutes to ensure they were heated evenly (and also dumping heat evenly).
The radiators themselves are pretty damned efficient at what they do. Despite being in full sunlight, the crew of Apollo 13 were freezing because most of their 1960's high heat output electronics was switched off. Instead of having to deal with that heat, the radiators were only dealing with sunlight resulting in a very cold (but still habitable) cabin.