Copy Data from Workbooks Sheet1 to Master Sheet - excel

Question

I have macro, which copies data from selected workbooks' Sheet1 to this main workbook's Sheet1 in last row. For small number of files, it is fast, but when I select more files (say 20), it breaks and excel even crashes. How to make this more efficient as I am already using Application.EnableEvents and ScreenUpdating?
Sub Copy_From_Workbooks()
Dim numberOfFilesChosen, i As Integer
Dim tempFileDialog As FileDialog
Dim sourceWorkbook As Workbook
Dim loLastRow As Long
Application.EnableEvents = False
Application.ScreenUpdating = False
Set tempFileDialog = Application.FileDialog(msoFileDialogFilePicker)
tempFileDialog.Filters.Add "Excel Files", "*.xlsx?", 1
tempFileDialog.AllowMultiSelect = True
numberOfFilesChosen = tempFileDialog.Show
For i = 1 To tempFileDialog.SelectedItems.Count
Workbooks.Open tempFileDialog.SelectedItems(i)
Set sourceWorkbook = ActiveWorkbook
If ActiveWorkbook.Worksheets(1).Range("A1") <> "" Then
With ActiveWorkbook.Worksheets(1)
With .Cells(1).CurrentRegion
.Offset(1).Resize(.Rows.Count - 1, .Columns.Count - 1).Copy
End With
End With
End If
With ThisWorkbook.Worksheets("Sheet1")
loLastRow = .Cells(Rows.Count, 1).End(xlUp).Row + 1
.Range("A" & loLastRow).PasteSpecial Paste:=xlPasteValues
Application.CutCopyMode = False
'ThisWorkbook.Save
End With
sourceWorkbook.Close
Next i
Application.EnableEvents = False
Application.ScreenUpdating = True
End Sub

Answer 1

You set a variable for the source workbook, but do not use it.
Use With blocks so you don't call the referencing object over and over and over.
Write the values directly as opposed to using the slower copy/paste.
For i = 1 To tempFileDialog.SelectedItems.Count
Set sourceWorkbook = Workbooks.Open(tempFileDialog.SelectedItems(i))
With sourceWorkbook.Worksheets(1)
If .Range("A1") <> "" Then
Dim valRange as Range
With .Cells(1).CurrentRegion
Set valRange = .Offset(1).Resize(.Rows.Count - 1, .Columns.Count - 1)
End With
End With
End If
With ThisWorkbook.Worksheets("Sheet1")
loLastRow = .Cells(Rows.Count, 1).End(xlUp).Row + 1
.Range("A" & loLastRow).Resize(valRange.Rows.Count,valRange.Columns.Count).Value = valRange.Value
'ThisWorkbook.Save
End With
sourceWorkbook.Close
Next i