Never! Updates yes, reinstall- NO!
I have had macs since 1993 (five of them) and never had anything go bad on them (knocking on wood right now!) except a powermac 5300 school edition which had one recalled problem (can't remember what it was, but Apple paid for it)
In that time period my brothers and sisters, who have owned about the same number of PC's, have reinstalled about a dozen + times and had four hard drives, three modems, three mother boards and countless other things go wrong with them. I love my Macs!
I went over a year without my current iMac needing a restart (minus restarts with updates)
I have had macs since 1993 (five of them) and never had anything go bad on them (knocking on wood right now!) except a powermac 5300 school edition which had one recalled problem (can't remember what it was, but Apple paid for it)
In that time period my brothers and sisters, who have owned about the same number of PC's, have reinstalled about a dozen + times and had four hard drives, three modems, three mother boards and countless other things go wrong with them. I love my Macs!
I went over a year without my current iMac needing a restart (minus restarts with updates)