You should be fine up to around 1.4v vCore and 74°C Tcase, which is the temperature of the CPU package, not the cores. Those are usually 5-10° higher so aim at below 80-85°C on the cores. This is the temperature Intel publishes as a safe temperature for long term use.)
Depending who you ask, values of 65-80°C on the cores are the safe limit.
And even then there is the so called "TJmax",the temperature at which point it gets critical. Those are usually around 95-105°C, depending on the model and are the point where the chip starts thermal throtteling