Thanks for the info all!
For those who wanted to hear the responses, coins can continue to tone after being slabbed. The unanimous recommendation was to use Intercept Shields to protect coins from unwanted toning. Also, best not to store slabs or coins in hot, damp places.
Coin toning after encapsulation by NGC
I'm relatively new to collecting and wonder if coins encapsulated by NGC and PCGS continue to tone after encapsulation. Any feedback is appreciated