First, why would you do this? Next, there is a reason they make special fixtures for the bulbs. They have to stay on for long periods of time and desk lamps and house lamps are not designed to be on 12+ hours a day 7 days a week.
Its BECAUSE I want to know !! I have proper lighting for all my chams and other reptiles. I'm looking into extra lighting to have back up for upcoming winter.
I would just save up and get the proper fixture. the cone fixtures aren't super expensive and are made to handle the longer periods of time on. That is why they have the ceramic base instead of plastic like desk lamps.
I do agree, we just have spare heat bulbs everywhere and last winter our hot water ran out for a day or two so we had no heat. If I needed to use an extra source for a few hours its nice to know if these would burn my house down or not lol
I have used desk lamps (removed the "arm") for a uv spiral bulb and also am using one now with a 40 watt incandescent as a heat lamp. I have been using it for 4 months 12 hours a day with no issues. I don't agree that they can't handle it so long as you're not exceeding the maximum wattage for the lamp. But I would make sure the lamp has a ceramic base, which most of them do these days. What is the difference between a metal "reptile" lamp with a ceramic base and a metal "household" lamp with a ceramic base. Seems like one and the same to me. Just like we don't need to use a "reptile" bulb for a basking spot when a regular household bulb is fine.
The only thing I wouldn't do is use a ceramic heat bulb with anything but the wire fixtures designed to hold them.
I know many people who use normal desk lamps for heat bulbs and compact uv bulbs. As long as you do not use a ceramic as mentioned above and do not go over the wattage it says for that fixture it will be fine.