Beware using 3rd party spreadsheets to forecaste components and maintenance
until you have thoroughly tested it and are completely happy with the answers. Not testing could leave you open to overflys etc and possible litigation with little comeback if the spreadsheet proves to be faulty in any way.
I am not putting down the time and effort of the authors of these sheets,as they do provide an inexpensive and efficient solution when properly written. They take a lot of thought/care and effort to get right.