That is the kind of information I wanted to make available.  Unfortunately in the past I have made the same mistake that the writer did and db touched on. The reason many knowledgeable people come to this conclusion is it is hard to find good curves on batteries.  On one trip I carried 8 D cells and they ran out of power.  Last year I carried 18 AA’s (lithium) and they lasted. Now that I have measured the lithium batteries and can see that the voltage does not droop I will use sets of 8 rather than sets of 9 and will only take 2 sets of 8 lithium batteries. I have also cut the wires to the lights on my detector.
If you use 8 alkaline batteries in series (AAA’s or AA’s or C’s or D’s) when the batteries are 35% used up the voltage will drop below 10 volts and the detector will not work well. Most detectors shut off when 50% of the batteries are used up.
If you want to use alkaline batteries put 10 in series.  10 in series will last about as long as 2.8 sets of 8 batteries in series. 
The article has a nice comparison of the current draw between different detectors.  This is most likely the current draw listed in the manual and makes a way to compare different detectors.  I think Lowrance/Eagle lists the highest current the detector will draw.  I come to this conclusion from my own measurements.  For example Zski’s Lowrence X4 is listed in the article as drawing 170mA. Back one page in this thread is my measured values for that detector.  At less than 70 Ft it never draws more than 100mA.
The battery holders that the article suggests will work and I have used them.  I found that they have many (4 per battery) pressure connections that will increasingly have voltage drop across them.  If that is what you are using you may want to replace them every couple of years.
Advantage of Lithium Batteries
1      Much lighter per hour of detector operation
2      Cheaper per hour of detector operation
Advantage of Alkaline Batteries
     Better for the environment