In the old days the actual time would slow down instead so you were running through glue. You prefer that??
Simple answer: Yes. With delta timing you don't actually know what the hell your end-user will get to see. Not knowing what you're presenting means you've failed as a designer, regardless of how technically superior that fancy-pants timing code makes you feel inside your own head.
And, of course, if you're honest about your required specs then slowdown won't be an issue.