Of course they are working.
When exceptional precision is needed use a Temperature Compensated Crystal Oscillator (TCXO) or place the crystal in an oven that held the crystal at a constant temperature, creating an Oven Controlled Crystal (XTAL) Oscillator (OCXO). The TCXO capabilities were typically not quite as precise or accurate as the OCXO, but since TCXO’s operated at much lower power and could be smaller in size, they satisfied much of the demands. Now a days you may find some TCXOs with Electronic Frequency Control (EFC) have holdover capabilities up to ±0.10 ppm for 24 hours over the operating temperature range.