Should I replace the chain at 90k miles. I don't see much if any slack at all....but I have a brand new chain with the guide....

I have the head off and its sitting there until I get it back from the machine shop. In the mean time should I replace it for good measure seeing as I have a new one or leave it alone?

How long do you think it should take me from here?

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k