It's not uncommon in sensitive analog systems to do something like this, ~but I haven't seen anyone doing it with an FPGA yet~. Very old analog systems (that w

It's not uncommon in sensitive analog systems to do something like this, ~but I haven't seen anyone doing it with an FPGA yet~. Very old analog systems (that were a lot more temperature-dependent than modern analog circuits) often were contained in small ovens, and an intermediate step between a normal oscillator and an atomic clock today is to use an oven-controlled oscillator. In both cases, they keep the ambient temperature on the analog devices at 40-50 C to make sure that they operate at a stable temperature regardless of ambient temperature. Edit: See the sibling comment - someone has found a reasonable circumstance to do it!