Multiple bulbs = smart move as bulbs tend to burn out.
Another suggestion is to use the small ceramic heaters that work on 110VAC (like 5 or 6 inches wide and high and about 4 inches thick.
Most have a crude thermostat and 2 speed fans but work very well with the advantage of blowing the warm air throughout.
Generally rated at 1500 watts in max setting.
The concept is a ceramic heater up front with a 5 x 5 muffin fan to circulate the heated about.
LOL, I had one installed in my well and come spring the water rose and the ceramic heater was totally submerged.
I dried it off and to this day it still is operational but I only use it in closely supervised situations. Never unattended. (like alongside if working outdoors on the tractor)