How would you know by looking at it if the weld took or not? A little stickiness looks the same as a solid weld, the only way to know the difference is to turn the billet on its side and hammer at it to see if it separates.
The etchant lasts a very long time unless you manage to pollute it by getting some copper or brass etc in it. It gets weaker over time but adding some fresh solution to it can spiff it up although its probably smarter to just replace it every year or so (depending on how much you use it) ...
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