Arduino Mega2560 and SD card module read and write

Projects General Guidance
1

I'm currently having a project which reads, voltage and current then computes for power, peak power and total energy consumption of an appliance/s.

One feature of my project is that the user can save and read readings of peak power and total enrgy consumption which is stored in a 1GB micro SD card. The user can save and read the readings anytime he/she wants.

My question is how much can arduino read and write take with this kind of memory and process?

here is my code of how I write and read text in a file.

Write:

int WriteToFile(String text){
  if(myFile){
    myFile.println(text);
    return 1;
    }else{
      return 0;
     }
}

Read:

void Read(){
  myFile.seek(0);
  char cr;
  for(unsigned int i = 0; i < linenumber;){
    cr = myFile.read();
    if(cr == '\n'){
      i++;
      }
  }
  while(true){
    cr = myFile.read();
  if((cr == '\n')||(cr == '\r')||(cr < 0))
    break;
    lcd2.print(cr);
  }
}

Im using the catalex micro SD card module and Arduino Mega2560 MCU.