>> Ron almost always has excellent advice but I think he's not totally
correct in this case:

One strut can't do more work than the other.  The struts are filled with
compressed gas and they push as hard as the gas pressure lets them.  If one
has lots of pressure, it will push harder than the other, but that's as far
as it goes.

You may replace one strut only to find the other was near the end of its
life anyway, but there can be no causal relationship between the replacement
of one strut and the wearing of the other.  <<

This does not make any sense, physics 101 will tell you that using 1 strut
instead of 2 will double the weight on the good strut. It will probably last
less 1/2 the original intended lifespan.

Bryan