I can attest to what Jesse says. I have 8k bulbs in low and high. For all purposes where high beams are needed, (for my driving) the warm up isn't so much an issue.

The 5-6 thousand Kelvin range is where the eye is most receptive, so those will certainly appear brighter on the road.

No issues with heat whatsoever. No bulb warning, nor firing issues.

However, if your courtesy fog lights are enabled, you may notice a failure to trigger on occasion with HID.