In Virginia and picked up our first nuc last night. We have the entrance reducer on to help support the hive as it grows stronger. My mentor also mentioned it’s best to have it on during the dearth when the nectar runs out in mid July to counter robbing. Then I guess it goes back on for winter.
So curious when to take it off of the new hive/nuc? When the frames are all built out? Then on for the dearth and off for the fall nectar flow?
Congrats on your 1000s of new best friends! 
It’s great that you have a mentor to support you, and as a naturalist yourself I’m sure you will enjoy being a beekeeper! My hives are all reduced with a solid (no notches) length of wood that simply sits in the middle, leaving two openings on either side. This helps the bees with their efforts to convect air through the inside to regulate temps. They set up a fanning brigade in one side and out the other - it’s marvelous to watch! To follow your mentor’s advice, you can keep two different lengths on hand for seasonal needs.
I learned about this by watching a film that @JeffH has often posted called The City of Bees. For some reason I can’t locate in the search to paste it for you, but Jeff will be along to help shortly I’m sure 
By the way, I tried to recategorize your post into Beekeeping Basics for you so you’d get more responses. When you start a post the default is ‘Uncategorized’, which is kind of a desert & not the best place if you really need answers. But the ‘recategorized’ function seems to have been removed - @KieranPI @Freebee2 is it just me?
Ah, thanks, I have categorized per your advice.
Thx also for the video suggestion.
I can see why 2 notches may be better than one depending upon circumstances! An interesting idea.
Hi Eva, many thanks 
I’ll also link the other one that I like to promote. That one shows a queen mating in flight, with the drone “popping”, = instant death.
