I always keep a drop kit as back up because of the usual issues with pens. I looked at apera pens a while back, the replaceable probe is attractive but it costs almost as much as their cheapest pen. You can still get a duffer if it’s been sat on a shelf too long and dried out, same with any of them. I am still tempted though and might get one to try at some point. The drops get to be a pain at times but they are at least accurate 
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