139K Miles on 2012 4.6 tundra trans, should I drain n fill or leave it as is till it gives out

Needs come thoughts, the tundra I bought has never been serviced on the trans it has 139k miles, I keep hearing mixed reviews weather I should drain and fill, or just leave it as is, to keep the natural debris it already has in it.
Long story short should I service the trans?

 

Drain and fill, no flush.

Do the diffs and if 4wd, xfer case while you are at it. And lube your drive shafts zerks.

 

^^^^ x2 on what he said

It would take about 3-4 drain and fills to do a 'complete' trans fluid swap. So, if you start now and do another every 30k or so you will have exchanged most of your original fluid out by about 200k and shouldn't have the associated risks of doing a complete flush.

 

Bought our Tundra with a shade over 140k, and no record of trans service. Fluid was very dark from the first drain and fill, so I have no trouble believing it was original to the truck.

I've completed 4 drain and fills between 145k and the current 190k. Every drain and fill has been performed in my garage with Toyota WS ATF, and the "back door" OBD paperclip leveling technique. I was very pleased to see the wonderful, red fluid which came out from the last service I did a couple weeks ago.

The transmission is running smoothly and I plan to continue with the drain and fills once every year moving forward.

Here's a great writeup added to the site earlier this year:

https://www.tundras.com/threads/2nd-gen-transmission-drain-and-fill-diy-how-to.137487/