Adding millis to LCD instead of delay, help?

Projects Programming
2

There is one task to do, so I would use just one millis-timer with one previousMillis variable.

You could count each time the millis-timer gets activated, and do different things for each number of the counter, perhaps also turning off the millis-timer.

You could combine a Finite State Machine with millis. To me that seems over-the-top for your project.

Is it 7 seconds one page and 7 seconds the other page continuous in a loop forever ?
Then you only need a millis-timer of 7 seconds and a counter that is 0 and 1.
Let's not call them first rows and second two rows, but let's stick to "pages".

int page = 0;      // start with page 0
unsigned long previousMillis;
const unsigned long interval = 7000UL;

...

if (currentMillis - previousMillis >= interval) 
{
  previousMillis = currentMillis;

  if( page == 0)
  {
    // show page 0
  }
  else if( page == 1)
  {
    // show page 1
  }

  page++;          // next page
  if( page > 1)    
    page = 0;      // back to page 0
}