Tundra Transmission Service

I have a 2015 Tundra 5.7 with the 6 speed automatic transmission. I have 55K miles on it. I cannot find in the owner's manual any mileage interval for automatic transmission service. My understanding is that it is a "sealed" transmission. Does that mean it doesn't require servicing? I tow an RV with it, maybe once a month, for maybe 150 miles give or take. I'm not really wanting to fool with it myself, and I'm willing to take it to the dealer for servicing, but I'd like to see something from Toyota that specifies the interval. I'm sure the dealer would be happy to take my money.