The 0 Buffer
Here's a Vim 101 thing that I went without knowing for far too long, so maybe it'll help you as well:
Say you have 3 lines of code ...
T-2000 John Connor's Foster Mom Random Policeman
And you want to replace the second two lines with the first. You might type
yy to yank
T-2000, then type
p on line 2 to replace
John Connor's Foster Mom with
T-2000 T-2000 Random Policeman
But if you go to line 3 and type
p again, you'll paste
John Connor's Foster Mom, because Vim replaces the default buffer with the previously removed line.
T-2000 is still available in that scenario – it's automatically placed into the
0 buffer. To continue to paste
T-2000, just type:
to paste from the
0 buffer instead of the default buffer.