I think the thing is any change to what's normal for you.

I've always had to use the superest pad known to man, from when I first started my periods. Never used tampons really as they just didn't cut it. And right from the start, I've always had 2-3 days of really heavy bleeding then virtually nothing for a day and then regular bleeding for a day. And despite the fact this has happened for 25 years, the day of no bleeding still catches me out and I think I'm done and dusted.

I think mine are still the bog standard 28 days (they were when I conceived DD2) but I haven't been monitoring.