Re: How old?
I think it's a personal preference. I set the example by hand washing/waxing my roadster and SRT6, and do the same during the summer to my A6 (it looks pretty darn good for a 2003 with 152k miles). I have to nag my 19 year old son to wash/wax his 2007 XF -- the last two times I started it myself and shamed him into helping. He likes having a nice car but is too lazy to REALLY care for it. On the other hand, I bought my 17 year old daughter a 2003 A4 and she washes it 2-3x per week and waxes it at least weekly in the summer. Just different kids. Different personalities. Same difference in their homework effort, btw.