With normal, intermittant use, you will likely rarely burn out a bulb. I think you'll feel the bite of buying batteries long before you worry about lamp assemblies.

BTW, you should be buying batteries online in bulks of at least 12 to get reasonable prices. Best prices around $1 ea. for less known brands, worst case $18 for 12 (Streamlight: very reliable, good performance). Prices prior to shipping.

-john