Question about tire tread safety levels

My tires tread is on the 4/32 of inch part of a ruler or close to where the change soon part of this image is:


https://qph.fs.quoracdn.net/main-qimg-e27d49a98c37121ace6c43edf9ad90a4

One is flat at that level (is 5 yrs old) and the others are just worn down to that same level (one is 5 yrs old and the other is dated from October 2019). Should I go ahead and just get them replaced or find out if it needs to be patched (for flat) instead? If so how long do you think I would have until the tires tread gets less than 2/32 of an inch or where it's not safe to drive anymore? WOuld hate to waste 2 days at discount tire if you guys can push me in the right direction th efirst time around...

Just replace them.

I see you posted here as well as Car Talk.

Same answer as before. It makes sense to replace them all. It doesn't take that much more time to do 4 new tires than it does to repair a flat. It's the waiting that takes most of the time - and Discount Tire offers appointments. In my case, I was in and out in a half hour (one tire, but still!)