Macro Performance - Speed Tuning

I run a simple macro loop to clean some data across nine columns. The purpose is to collapse the data in the columns so that column 1 has the first value found in that row, for the set of columns. For instance, if columns 1-4 are empty, it deletes / shifts everything left until the first column is not empty. Then it goes to the next row and repeats. Data can range from a few rows up to 6000.

[I have a period in the data as the cell content to evaluate]

Sub A_Rollup_collapse()
StartT = Now

Dim Col As Integer
Col = Range("IV1").End(xlToLeft).Column - 9
LastR = Range("A60000").End(xlUp).Row

Application.ScreenUpdating = False
For R = 2 To LastR
Do While Cells(R, Col) = "."
Cells(R, Col).Delete Shift:=xlShiftToLeft
Loop
Next R
EndT = Now
Application.ScreenUpdating = True

msg = "Done. Duration: " & Format(EndT - StartT, "h:mm:ss")
MsgBox (msg)

this macro (B) runs after another macro (A) that populates the nine columns with data using vlookups. Macro (A) It builds out a chain of information from col 2 to col 9, converts to values etc. Nothing odd.

When macro (B) is called right after running macro (A), it can take about one minute for 500 rows of data.

When I save and close the workbook, reopen it and run macro (B), it only takes one second.

When I insert a ThisWorkbook.Save between the two call statments, macro (B) still takes over a minute.

A minute is not too bad but when I'm dealing with thousands of rows, the difference is more like 30 seconds vs. 9 minutes which is a problem.