I''de like to think that whatever rendering he is doing will
cost a magnitude more than any fps calcualtions that might
need to be made. This being the case their would have to
be alot more programming before it made any diffrence.

So the cost of a few casts is nothing. Especially at the
lower framerates where their is a big diffrence between 9
and 9.99999999. At the higher framerates it will matter
even less.

If you only wat to update is at a specific interval I recommend

if ( frames % 10 )

so it only executes once every 10th frame.