"...And you will certainly know that I, Jehovah, am your Savior..." (Isaiah 60:16)
You'll see the Bible clarify this "milk" as "resources" at Isaiah 61:6 in that marginal reference after the word "nations" with the little "+" symbol above; One of those resources being modern technology - the Christian congregation has employed it to make an outstanding website jw.org. This milk is very conducive to making strong spiritual bones that we are very thankful for so that we may stand up straight and lift up our heads at this system's conclusion. (Luke 21:28)
Milk is easy to drink. So, for fear of drinking too fast and squirting it out our nostrils we also get direction to slow down and think about it:
This milk is being used by so many everyday for their physical needs, why not use it for spiritual ones as well. We eagerly await Jehovah's day when he will clean out the fridge and we'll be fed in a more direct way.
There may be some in your congregation that are lactose intolerant or they may like a different flavor. When this happens remember to keep putting up with one another and work together in the spirit of meekness. (Ephesians 4:2)
Until then, may I offer you a glass before the expiration date...
... this one's flavor is STRAWBERRY! ;)