Correct. I've been wearing retainers everyday (from after dinner till the next day, take out during daytime) and already felt a bit of shift. This is one year since removing braces.

My cousin teeth totally crooked again after 3 years but she told me she didn't really wear the retainers properly.

I wear at night, take out in the morning. It's fine. Slight discomfort at first, but then you get used to it.

Price to pay for straight teeth lo.