I'm out of memory? Is the next thing up the Mega644P?

Using Arduino Project Guidance
13

PeterH:
By the way, your implementation of timer() does not handler millis() overflow correctly. To handle overflow, you can code it like this:

if(millis() - lastTime > interval)

{
    // interval has expired
    ....

Mine should do the same thing. My code is:

//keep track of time and handle millis() rollover
boolean timer(unsigned long timeout)
  {
    return (long)(millis() - timeout) >= 0;
  }

and then when I need to time something I do something like this:

last_valid_data = millis() + 2000;

and then I can just call timer like this:

if(timer(last_valid_data))

which I believe mathematically is equivalent to your code. I could be wrong though. I took calculus twice in college and still only squeaked out a "C" grade so my math may not be up to snuff.