My last terminal facility it was common to work 15 frequencies plus 2 clearance frequencies for satellite airports in a single radar position. If it started to get unworkable for one person, we'd split that into one position with 5 freqs and another position with 10 freqs. It was designed for 7 individual positions, but 1-2 was the most common and I only saw 3 open no more than 4-5 times.
Flying near SAT one day with another controller buddy, the SAT controller had enough and said on frequency, "all right everybody you're going to have to listen up because I'm working THREE frequencies here." The other guy and I turned to each other and just started laughing.