I haven't checked too carefully, but trail files are generated much the same way as mapkeys are recorded.
Unless mapkeys go away, trail files are not likely to go either.
As far as running trail files, it is important that the initial conditions for the recording of the trail file are reproduced exactly when trying to re-run the trail file. It's the hardest part.
I have used them, debugged them, and created software to generate them. While a large amount of text in the trail files is commentary and not used to create or manipulate Pro/E objects it does take time to see what is going on with them and to separate out the text that is actual commands.
The move from a menu structure to the current interface certainly makes it more of a challenge.
Three seconds is a bit too long for trail file delay - the reason Windows says Pro/E is unresponsive is that Pro/E is not servicing requests for info from Windows because it is busy running (slowly) the trail file and doesn't wish to be interrupted.
The model player is not intended to be used as the equivalent of a video editor - allowing one to cut off the action mid-play. That is done by copying the trail file contents from the beginning to where-ever a safe break is found near or just before you want to stop. If you do a binary search then in 16 tries you could get as close as you want in a trail file of 65,000 or so lines. That's a long trail file.
It is very interesting and educational to learn what is being recorded as it gives some insight into how PTC solved various problems. One may not like the solutions, but if the trail files are to be of value, learn you must.
I've only had occaision to run a clean file from the top. A drafter did an entire drawing, including making ink plots on mylar, but the next day could not find the file. I looked a bunch of places and then into the trail file. There was no Save command and it ended with Quit? Yes. I removed the little bit about the plotting and the quitting and in about 15 minutes it had recreated the drawing exactly. I asked where the other seven hours and forty-five minutes went from the day before as this was the only thing they worked on.
You'd think I would not get the -glare- from someone who's bacon I had just pulled, crispy from the fire, but maybe it was less than would otherwise have occurred.