Does trans fluid wear out

Update.. Trans started a downshift slam every once in a while while cruising in o/d. Also A slow take off now and then and a bump on the downshift at 5 mph when coming to a stop. Someone mentioned limp mode being 3rd gear, and with the tcm to pcm problem I started reading.Led me to believe the pcm lost info or got wrong info when when I left it running and it got warm. Disconnected the hot cable and grounded it to the negative post, Lost the code and check engine light. Drove it and it hammered a few times the first day ,then once the second day and the last few days it has been fine.I drive 100 miles or better every day.I think the tcm or pcm relearned what was causing limp mode and fixed itself. Could this happen. I know dealers reflash them when they rebuild or replace them. Could I really be this lucky? Is it even possible?