For valves, an Irritrol 205 will be repairable forever, and they are not known for cracking. For heads, the field is wide open - you replace entire heads, not just the innards, unless it happens you have the exact same head as the one being replaced. For a controller by Hunter, consider the Pro-C, as it has some additional features that can pay back the extra investment.
I must disagree since "repairable forever" will outlive you.;