Funny, they didn't post that in owner's manuals I got. Nothing mentioned. Regardless, you can go longer, go by fluid color. Fluid will be red, then go orange then brown. Going 60,000 will have oil just getting orange barely if you don't abuse trans or tow. I change at 60-70K and the trans lasts forever. I don't change filter either. If something breaks like that you can pretty much be sure it will be something that would've broken even if brand new fluid kept in it all the time. Every Ford ATX I've fixed on my stuff went down over crap designed parts............
If fluid changes color faster change fluid faster.