I have some DF towels I got last summer for when I used Zaino on my 350Z. Some of the towels have some stains on them and are looking alittle wore out. I only used them to take wax and polish off. How long are towels for using on paint good to use still? I just want to make sure I am not causing any scratches on the paint from the towels I use. Also, how long are waffle weave towels good for if they are still looking good? Thanks