13dd8344_ing_guidelines__best_practice___Rationale
[Good practice] When numbering similar types of files or sequences try to anticipate maximum numbers [Rationale] 
If you build in limitations e.g. myfile02.txt then you may have to rename files when the number of files exceed say 99 e.g. myfile187.txt otherwise lists of files will be difficult to order.
DAM » Blog Archive » File naming guidelines (best practice)
Rationale