dude, in both these accounts of this parable the servant who buries the Master's riches is evil, wicked and unbelieving. i'm pretty sure he's not a Christian who receives small reward in one account and an enemy of God dying in his sins in another. Matthew has him cast into darkness where there is weeping and gnashing of teeth and Luke has him put to death; aren't these the same thing, the second death
the cowardly, unbelieving, abominable, murderers, sexually immoral, sorcerers, idolaters, and all liars shall have their part in the lake which burns with fire and brimstone, which is the second death.
(Revelation 21:8)
i realize that the variances in the gospels indicate that probably Christ preached the same parables multiple times, and the apostles are likely recording different 'versions' of some things because different instances were recalled to their minds when they wrote. and i realize that you can argue this, and say that at some point Christ started speaking of the kingdom of heaven instead of the kingdom of God, and that pivotal point represents when Israel as a nation rejected His offer of a physical kingdom on earth, so He changed His message and began preaching a spiritual kingdom for the interim.
but to my understanding, you've just pointed out another example that challenges the supposed difference between the kingdom of God and of heaven - the same God is King of both heaven and earth. i don't see why a distinction should be made? in Luke, this is immediately followed by Christ entering Jerusalem being announced as King, and in Matthew it's immediately followed by Christ speaking about when He will come to sit on His throne as King and separate sheep and goats. so in both accounts - whether they use the term kingdom of God or of heaven - the next thing we read is about Christ as King. in both accounts, this is a very much tangible kingdom, and also very much not a kingdom of this world: He's King of Israel in Luke, tho by the measure of the world He's nobody; Rome rules the city. the truth is that He is though, and is come in meekness to work true, spiritual salvation of His people. in Matthew, He's speaking of when He comes in His glory - not as though He only at that time becomes King, for He is forever - and He speaks of separating sheep and goats, which is a separation to spiritual life and spiritual death, so it is as an heavenly thing. and there, He says this:
Then the King will say to those on his right,
Come, you who are blessed by my Father; take your inheritance,
the kingdom prepared for you since the creation of the world.
(Matthew 25:34)
what's this kingdom? it's given to His sheep. it's their inheritance. is this maybe what you're speaking about when you talk of an earthly kingdom, different from the kingdom of heaven? i understand the heavenly and the tertiary kingdom to be one and the same kingdom, now partially revealed, later fully. something to think about. things we will not understand fully until they come.
i don't disbelieve in the millennial kingdom. i hope you don't think that of me. but this is one of those things about 'classical' dispensationalism that just doesn't smell right to me -- to me, personally, it is much like issues i take with covenant theology, their habit of inserting 'implied covenants' where nothing in scripture ever speaks of it, for example what they call the covenant with Adam. it just seems all an imaginary thing that was necessary to add in order to patch a hole in the thinking of that theology, like Einstein and the cosmological constant. for Einstein, the truth hadn't been really understood, so going by some assumptions that turned out later to be faulty, he added this number to his theory. to me, the same situation is at hand with these two major branches of Christian thought - there is understanding both lack that so that hey fail in points, and are incomplete. God is infinite; knowing Him is infinite, and it is true life - it doesn't surprise me that our human meditations on Him are imperfect. we will fully know one day though; that is our hope and our promise from Him 
i appreciate being able to discuss it without throwing stones at each other btw ♥
Remember, the four gospels are not their versions of the story. They were moved by the Holy Spirit to write exactly what God meant to communicate. There is a purpose behind the two terms.
Let’s do a comparison between the gospel of the kingdom and the gospel of grace.
Matthew 24:14 And
this gospel of the kingdom shall be preached in all the world for a witness unto all nations; and
then shall the end come.
Has the end come? Of course not. This kingdom gospel will be preached in all the world during the tribulation. The King is coming. His kingdom is literally at hand.
Paul’s gospel of grace has been preached in all the world. Has the end come? Obviously, two different messages. Some believe they can usher in the kingdom by getting Paul’s gospel out to all the world. News flash...it has gone out into all the world.
Colossians 1
5 For the hope which is laid up for you in heaven, whereof ye heard before in the word of
the truth of the gospel;
6 Which is come unto you,
as it is in all the world; and bringeth forth fruit, as it doth also in you, since the day ye heard of it, and knew the grace of God in truth:
Verse 23 If ye continue in the faith grounded and settled, and be not moved away from
the hope of the gospel, which ye have heard, and
which was preached to every creature which is under heaven; whereof I Paul am made a minister;
Romans 16
25 Now to him that is of power to stablish you according to
my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery,
which was kept secret since the world began,
26
But now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God,
made known to all nations for the obedience of faith:
1
