Electronic – What lamps are out there that don’t flicker and give off warm light (like incandescent)

Most light bulbs have a number of service hours designed in. This is achieved fairly accurately and on purpose during manufacturing. Consumer grade light bulbs burn out faster and the awful truth is that in that way the manufacturer ensures it can keep producing the light bulbs and make money. The main cause is the tungsten filament slowly evaporating until it gets too thin to carry the current. The trick during manufacturing is to etch the filament to a carefully designed thickness so the lifetime is reduced programmed.

The origins of programmed life light bulbs began with the Phoebus Cartel in 1924.

There are also light bulbs with a special stronger filament (basically they skip the 'etch-cycle'), these are for use in high reliable applications and last longer. They are commonly used in places that are hard to reach and are more expensive. Not sure about the proper name of these light bulbs. Because of the extended life time these bulbs are more expensive as a manufacturer has only limited room for producing spares. (What need is there for spares if the bulb doesn't fail?)

Where Australia and EU banned the consumer grade bulbs, the strengthened filament is not banned because of its specialized application. The latter type is just not available in your regular shop around the corner.

I'm not sure this is so mich an "original" answer as a combination/explanation/redinement of the other 2 already posted answers, but I'll try to help a bit.

1. As transistor pointed out in the question comments, the 'bulb'-life impact of rapid switching on several varieties of lights is discussed in some detail in If I flick the light switch on and off will it damage the light?

2. Autistic, Rothloup, and 2 posters in the other thread are all right about 'dimming' the incandescent greatly improving bulb life.

   • I would recommend using an inductor in SMPS buck-converter arrangement as likely being the most efficient (be careful though, the efficiency of that one inductor could surprise you, incandescents have a very non-linear response & tend to respond well to under-voltage drive).
   • While the buck converter could arguably be run on from non-rectified ac current, I would personally recommend using rectified & conditioned/smoothed DC (for predictable performance), and a pwm management that never cycles slower that 40KHz (so you don't have to hear it 'sing').

3. You should definitely replace the relay with solid-state components.

   • At the least, a triac or optoisolator/'solid state relay' can switch your load faster than a mec. relay & love longer.
   • Better by far would be using a bridge rectifier & a capacitor to convert your input to smoothed/conditioned DC, then use a power MOSFET (if you get a 'logic-level drive' one, it won't even need any external buffering transistors) to run the aforementioned buck converter.

4. Putting it all together, if you PWM a buck converter, with solid-state switchgear, to keep the light somewhere between 'just warm' and 'hot, but barely glowing,' you should be able to maximize your energy efficiency, component lifetime, and the precision/stability of your incubator's temperature control.