I have quite a bit of "heuristc" algorithms that I'd have a pretty hard time to "slow down" consistently... so I just slow donwn the framerate.
Of course... But as Ross C showed, taking that shortcut also means that your program simply won't work at all on some computers.
If nothing else, you should consider using a 'normal' frame rate (e.g. 85 or less, depending on resolution) and use that as your default, rather than an artificial rate that won't be supported in hardware by 99% of the systems out there -- you'll run into a lot less problems that way.
You could still slow down framerate from that point on to slow things down more, but starting at 150 doesn't appear to be the best choice.