Custom delay time is a great idea. Why stop at 5 minutes? Does not make sense.
To add the ability to adjust time in Minutes AND Seconds is just more development work. Not a big deal, just another task that needs to be prioritized. Remember, each "wish list" request like this is really;
>modify core software on the A+, test, debug, fix, beta release, beta test, debug, fix, re-release beta, repeat as needed, release
>modify LCD User Interface test, debug, fix, beta release, beta test, debug, fix, re-release beta, repeat as needed, release
>modify Web User Interface test, debug, fix, beta release, beta test, debug, fix, re-release beta, repeat as needed, release
>modify IOS App test, debug, fix, beta release, beta test, debug, fix, re-release beta, repeat as needed, release
>modify Android App test, debug, fix, beta release, beta test, debug, fix, re-release beta, repeat as needed, release
So at a minimum that single change becomes 5x8=40 discrete tasks or software Levels of Effort and that is being generously conservative in an estimate, it is likely much more.
It would be awesome if each of those tasks were only an hour each, but I'll wager it's more than that, but even best case that is 40 hours minimum worth of work.
All of that, and assuming you don't 'break' anything else while doing it.
So yes, we want adjustable timers that work in seconds, minutes, hours, maybe even days (though personally I'm not able to envision that need given the current time of day/day of week options), but there is nothing trivial or inexpensive about getting it done.
Having said all that, I'm ready to have it today !!
Squeaky wheel gets the grease. Keep making noise about your preferred wish list items.