Struts do need to be replaced in pairs. They deteriorate very gradually
and are hardly noticeable but tend to need replacement after 50K miles.
This will depend on a lot of external conditions to say when exactly
they need replacing (see the Monroe FAQ below).

Do check with your service manager to see if the dealer is willing to
consider it as a good will replacement, but I doubt it after the
bump-to-bump warranty expires. But if it leaked at 96K km then they
should have noticedit -- if it indeed leaked at the time.

$750 CDN sounds a little steep for two struts. Consider getting
Bilsteins with a desired level of damping and new mounting parts. You
will need an alignment afterwards.

http://www.monroe.com/tech_support/tec_faq.asp#2

Q: How many miles do shocks and struts last?

A. It's hard to say how many miles a shock or strut will last since the
amount of work they do (converting suspension motion to heat) varies by
road conditions; however, Monroe suggests that they should be inspected
by your local Monroe Expert Plus dealer or any ASE Certified Technician
once a year, or every 12,000 miles. For example: Unlike a tire, which
rotates a specific number of times per mile, a shock absorber or strut
may compress and extend several times per mile on a smooth road, or
several hundred times per mile on a very rough road. There are other
factors that affect the life of a shock or strut, such as, regional
weather conditions, amount and type of road contaminates, driving
habits, loading of the vehicle, tire / wheel modifications, and the
general mechanical condition of the suspension and tires.

This is a chronic problem with 2001 & 2002 Civic's and 1.7 Acura's.
You're lucky that you got 100,000 Km out of them. Often people,
including myself, have had to have the struts replaced after the first
30,000 km.

I would most certainly go after the dealer to have them replaced. They
were more than likely leaking at your 96k service interval. There is
also a TSB out for these struts because of known defects.