The re-entry period is often limited in time and in number of re-entries.
The re-entry format is very popular in multiple days tournaments, where you can play several "day 1".
Here is a 240 min re-entry tournament, with a maximum of 2 re-entries.
If you loose your chips in the first 4 hours, you'll be able to come back twice in the game.
If the tournament has multiple "day 1", for instance day 1A, day 1B and day 1C, you can register each day et accumulate re-entries according to the tournament rules. If the tournament is limited to 1 re-entry per day, then you'll be able to register 6 times maximum.