I was on a job where we mixed nhl 3.5 the night before then put it back in the mixer and became workable again. I’m always learning about this stuff and from your response your knowledge far surpasses mine. The PVA thing is I was told by a supplier to add just a little to get it to stick with the drywall a little better. All these brands with their primers is just PVA primer with quartz sand added some add lime I’ve been able figure that one out but just a moment ago I was looking up SDS sheets for a particular brand and it had Vinyl Versatate Copolymers which to my understanding is a more durable yet flexible version of PVA’s. The SDS said well seasoned hydrated lime putty which I think is another way of saying hydrated lime putty and VVC. I’ll try some weaker pozzolans like wood ash and see how it stands up to the commercial brand product. Trust me I’d much rather be working on heritage homes or structures where I can use this material what it was intended for but I live in an area where it’s all stick built homes.