Garbage Collection using VBA

Hello,

In some programming languages I use, garbage collection is taken care of automatically by the program,
in others, the programmer is responsible for this.

With Excel VBA, which is the case?

ie if I do the following:
Dim ws1 As Worksheet
Dim ws2 As Worksheet
Set ws1 = Sheets("Calculator Data Table")
Set ws2 = Sheets("W-Shape MC")
Must I do the following when I am finished with them?
Set ws1 = Nothing
Set ws2 = Nothing

Similarly with:
Dim MyRange
MyRange = "A1:" & Selection.SpecialCells(xlCellTypeLastCell).Address
Is the following required?
Set MyRange = Nothing