Quick response from a 1991 Civic (171k miles) (original) owner:

What I've seen generally is mixing different anti-freezes, even if they're
the same color, is a bad idea. Definitely do not mix a conventional Prestone
green with the OEM coolant, which may be the blue stuff at the dealer's.
Definitely do not mix orange with green, etc. (Of course the color coding
implies a particular, certain chemistry, hence the advice not to mix.)

Ideally, do a flush (which is just a drain, fill, drain, etc. a few times).
You can probably get away with just a full drain (including engine block
drain plug removed), but it doesn't take but a few minutes to go the next
step and fill and drain a few more times. I just used hose water for this.
Of note is that, when I  measured all the coolant in my Civic's cooling
system this past April, what came out matched exactly the capacities listed
in the manual. The point being that a drain, fill, drain etc. should get
darn near everything old out.

The drain and fill also removes a lot of sand-like sediment that can impede
proper cooling or maybe bind mechanical parts. Around a 1/4 teaspoon of this
came out when I did a drain and fill after about 2.5 years this past April.
That may not seem like much, but ISTM some of the passages and the water
pump clearances are small and could cause the aforementioned problems.
(Someone else might elaborate.)

Generic anti-freezes are said to cause water pump (bearing?) problems. I
can't say for sure, but I know I had water pump problems after using the
green stuff. Lots of folks have testified here to the same. Three years ago
I switched to the orange (after a very thorough flush). I have had no water
pump problems since. The water pump is currently 4 years and 60k miles old,
having lasted much longer than the previous one (or two). I'll replace it in
two more years, when I do the timing belt. I won't be hitting the mileage
spec.

About anti-freeze shelf life, from Havoline's orange Dex Cool site: "The
primary limiting factor in the shelf life of a coolant is silicate
instability. Since silicate will eventually polymerize to silicate gel, all
traditional coolants have a shelf life of about 18 months. Havoline Extended
Life Anti-Freeze/Coolant DEX-COOL is silicate-free and therefore can be
stored for at least 8 years without a problem, provided the integrity of the
container is maintained."
http://www.havoline.com/products/na/antifreeze_01_tech.html

For distilled water, I just buy a gallon marked "distilled" at the grocery
store. Dunno about the lab water. The grocery gallon is cheap and common
enough.

Suggestion: List the year, miles, and model of Honda you own if you have
more technical questions.

First, and most important, do not use any silicone/silicate
formulation.  If you have it in there now, you are ruining the water
pump seals.  Flush like crazy and fill with genuine Honda coolant.
Expensive?  You just won't believe what it costs to replace the pump.
The photomicrographs of the damaged seals show erosion caused by the
silicate.  Silicate is simply sand.

You might be okay with an OAT type coolant like Dex-Cool, but it has
it's own set of problems like sludge formation if the radiator gets air
in it.  So, overfill the bottle like Texaco recommends.  And check the
level often.  It will give you long life, but so does Honda's blue
formulation.

I have a minor in chemistry.  The lab water is first distilled like the
bottled variety, and is then stripped of the ions that remain.  This is
produced by a great big, stainless-steel expresso-looking machine,
right?   But, such pure water becomes a decent solvent, and tries to
dissolve whatever it's in contact with, much more than regular water.
"Nature abhors a vacuum."  So, if it were me, I would actually add a
cup or two of tap water depending on your local water hardness.

My car is 2000 Honda Civic Value pack (kind of in between a basic and a LX
regarding the trim, but no difference in engine) with 69000 miles on it. The
car is Canadian make.
Mostly, I put in highway miles from C'ville to Philadelphia.(520 miles
roundtrip)
Thanks a lot for the feedback.
I will do a flush and fill up with Honda Genuine Antifreeze. I am kind of
skeptical about adding a cup or two of tap water to that water though as
suggested by jmattis. The slightly better solvent property of the deionized
double distilled water compared to distilled water is almost a moot point
considering its usage as a mixture to the antifreeze. I understand that it
probably is a overkill. I might use it because its easy availability to
me:-)

SB

hell no. you CAN use the orange dexcool 100k mile stuff in the silver
jug. either way, you should drain, run regular water thru for 10mins,
drain again. THEN add a 50/50 coolant mix.

some peeps here may disagree with the orange dexcool recommendation and
suggest only honda coolant. your call. ive used the orange dex in a
variety of aluminum japanese gas engines over the past 15 years, and
have had NO problems whatsoever with anything.

i wouldnt, no.

i think that would even be better than regular distilled water!