1-3 years warranty for different led lights and models . If any defective items during warranty period , ,pls show us the bar-code number and picture of each light, we will check ,and ONLY if the quality problem , we will provide the replacements to you and ship them with your next order( for international business ONLY ) . 

We can provide free samples for all our valued customers . For all our new customers , the cost of samples will be returned in your normal orders.

Should be ok to replace the headlight cap. I have seen reviews on YouTube about LED's VS Halogens and Heat. In general Halogen lights are significantly (at least 100 Degrees F), hotter than LED's so it should be not be a problem. As long as you get a LED that has a built in fan, that will keep the LED temp down. Heat is what kills electronics over time. Your headlight housing (if you currently have Halogens) can tolerate several hundreds of degrees of heat. Hope this is helpful.

I have these for my low beams and another set on my fog lamps. No interference, no flickering and just a really well made and bright product.
I'm actually in the middle of testing testing other competing products, and so far these are the best bang for the buck. 

They are, in effect, single filament bulbs, so they are low beam or high beam, depending on the location they are used on the particular vehicle. With low beams on, only the outer 2 bulbs are powered. With high beams on, all 4 bulbs are powered. The low beams are well controlled and aimed wide at the road, while the inner high beams are blasting way down the road. They work quite well in this configuration.