The packaging for a self-contained LED lamp says:
Operating temperature -10°C +40°C
Allow to cool before replacing light bulb
Use the same kind of bulbs in lighting units with multiple
lampholders. Do not combine LED light bulbs and filament bulbs.
For indoor use only
Please compare the weight of the light bulb to be replaced.
Mechanical instability may occur if there is a difference.
Why can't you use different kinds of lamps in a multi-lamp light
fitting? All the lamps that are switched on at the same time on the
same circuit are (apart from ones on dimmers) effectively wired in
parallel anyway. I can see why a hanging light fitting might lean a
bit if you put a heavier lamp on one side than the other, but the last
instruction covers that.
(I have a 3-way R63 light in one room with 1 CFL & 2 incandescents; I
can't see why that's significantly different from the situation in the
kitchen, where there are 4 single R63 fittings wired close together,
using 2 CFLs & 2 incandescents.)
Also, why is the LED lamp unsuitable for outdoor use (in an
appropriate fitting) above -10°C?