The /help Documentation for /timer -h should be clarified. It does warn that multimedia timers use system resources heavily, but doesn't warn that it rations them by allowing only 1 at a time. I did find that warning in the v5.8 section of versions.txt but it would be great for it to be mentioned in /help too.

I thought I had found a bug where the -h switch stopped making timers become multimedia, until I discovered that it only happened while another multimedia timer was already running. Nobody else I compared notes with on this bug knew that there was a limit of one.

Code:
//timerfirst -h 1 5000 echo 3 -a first $!timer(first).mmt | timersecond -h 1 6000 echo 3 -a second $!timer(second).mmt | echo 4 -a $version $beta first $timer(first).mmt second $timer(second).mmt

This lack of warning causes uses to unknowningly have their -h switch silently changed to -m. With a warning they can know they'll need to either loop through all active timers to see if any of them already have the only allowed multimedia timer, or check the .mmt property after they launch the timer.