Nobody climbs with a hitch series, but it is one of the most useful knots to know. The "lore" is that the hitch series can always be made to hold because half hitch multiplies the holding power of the knot by a constant: i.e., the holding power is exponential in the number of hitches. If you prefer not to do the math (Plummer’s analysis is reprinted in Prusiking and the 1963 Speleo Digest), just remember that more hitches equals more holding power.
Hitch series are cumbersome because they take a lot of space
and they elongate severely under load, but they do hold. I've
been able to demonstrate this by climbing 7/16 inch PMI with a
2-inch (yes, two) Samson sling. I've also used hitch series to
hold several hundred feet of oil-soaked 1-inch steel cable hanging
in a well while I cut and spliced in a new section. As I said,
with enough hitches, you can almost always get it to hold.
The performance of any ascending knot depends on the diameter, material, construction, and condition of both the main line and the ascender knot sling material. It may also depend on exactly how one ties the knot. Your knot’s performance can easily differ from mine.