AITA for not letting my in-laws continue to be late for everything?

Married 16 years and my in-laws have never been on time for anything. Not just a couple of minutes late, usually 20-30 mins or more and they don't ever tell us they are going to be late.

On Halloween they were supposed to be here at 6:30 to go trick-or-treating, my kids are teens so they already had plans but cancelled to spend time with them instead. At 7:15 we called and they said they were '5 mins away'. 22 minutes later, they arrived without any concerns.

This inspired a new rule for me, I called it the 5 min rule. Basically, if you tell me you're gonna be somewhere at a time and aren't, after 5 mins I will leave. If we are meeting to eat or something, and you're late, we will order and eat without you, we will leave when we finish even if they are just getting there.

Tonight they had plans to take my kids out for dinner, they said they'd be here at 7. We talked at 2p and I reminded them of the new rule. At 7:05 they weren't here and had not called or anything, so I called them. They said they were 10 mins away. I told them to not bother with it, they tried to ask me to give them another chance since they live an hour away, and I said no way and stuck to it.

I feel like they are disrespectful by doing this and that they aren't valuing my time. AITA?