1st car - megane - first car, bought it because it was cheap (about 12 yrs old), junked it when the welding bill was more than the value (about 5 years later).
2nd car - astra H (lowest spec), bought it at 1 year old to avoid initial depreciation, had it for about 5 years, replaced (part-ex) when it started feeling like something wasn't right.
3rd car - astra K (highest spec), bought it at 1 year old to avoid initial depreciation, still have it (2 years so far), no plans to sell it at any particular time, I really like this car so I'll run it until there's an issue.
so I guess it's roughly:
buy: 1 year old
sell: 5 years later