I specially want to use delay() function over millis(). The only question is does delay() have a limitation how long it can last. Well, I am not planning to delay stuff for days. However up to few minutes it may well be needed.
I have used 15 minutes while waiting for a Peltier device's temperature to stabilize. Never had a problem. Of course NOTHING else can be done during that time.
Thanks, Paul! Nothing else happens is what I need.
delay() is as accurate as the system clock (a few minutes a day) and can delay up to more than 40 days.
delay() can certainly be used until millis overflows, so for a few minutes, it's going to be more than OK. That said, I tend to never use delay() beyond really short delays, like 100 ms or so, because in the meanwhile the program can do nothing else at all. But that's just me; if it works for you, go ahead and delay.