Max Safe Heatsink Temperature?

[HomelandReloaded]

Does anyone know how hot the heatsink can be allowed to get without damaging the system? I'm looking at ways to reduce the fan noise without overheating the components. The normal operating temperature seems to be about 43 centigrade. If I take the fan out, the temperature of the heatsink slowly reaches 60 and still rising (at which point I put the fan back in). Although 70 - 80 should be no problem for a graphics chip, it could shorten the life of other components that are in contact with the heatsink. I was wondering if any modders have some advice. The fan noise seems to be caused mainly by vibration, but also partly by the narrow wind tunnel that seems to be essential to keep the heatsink cool.