Fountains - To seal or not to seal in hostile apps

I transport, set-up, and maintain water features in my business.  The vast majority are concrete (or cast stone as the retailers call it) and it is pretty straightforward.  I am encountering more enormous limestone fountains now that Pierres & Terres de France has a local importer.  In Washington state, we have extreme temperatures in hot summers and cool winters.  It is milder here on the west side, but it is wet and can dip to freezing during 3 or 4 months.

The overall question is related to sealing.  I understand Maurizio has a pretty strong and straightforward answer for natural stone outdoors and it makes sense.  But what about in applications either submerged or regularly exposed to water, and also what about concrete?

What I have learned:
The concrete fountain industry overwhelmingly recommends sealing their products.

What I agree with:
Considering that many of these items are painted or stained (whether or not that is smart in the first place is a different debate,) a sealer applied and reapplied annually prolongs the inevitable fading of the finish.  Also, properly applied sealer stops or slows down freeze damage.  Some customers simply will not winterize their fountains, and the sealer seems to penetrate or at least hold together the very fine layer that would otherwise crumble and expose the aggregate underneath when the ice collects on the edges or finer points.  But in a constant submersion environment, especially with water beating down in places, it quickly "goes away."  So, it isn't armor, but it helps, kind of like wax on a car I guess.

What I dont agree with:
A panacea solution.  "Just seal it" is the mantra from the people selling it, but not actually experiencing it. If it works on their garden gnomes, it must work on their fountains.  Sealer is not waterproofer how they make it sound.  Only the most labor intensive way of applying a sealer will make it even close to how they (fountain retailers) say it will work.  This means two or 3 coats on each piece before assembly (you will not get 100% coverage of the inside of a bowl after there is a pedestal placed in the center.)  And during assembly minimizing abrasion where pieces are moved into place.  Easier said than done.  As an installer, we can do it, but forget a first time customer doing this.  For that matter, many customers who purchase concrete have somewhat of a budget and are not willing to pay us the extra 3 to 6 hours and wait for an extra day for the above mentioned process.  So we have resolved ourselves to passing on the recommendations from the manufacturer to the customer to limit liability, and hope for the best. :(  If they can't get reliable sealing close to where the problem area is, the water will migrate  from the uncovered spot and cause the damage anyway.

The only time we have ever made anything 100% waterproof is by applying a firestone rubber liner (ugly) or elastomeric (less ugly) to the inside of a basin on a larger job.  This is not practical aesthetically and near impossible on a $2000 or less 3-teir generic fountain where every piece is small, curved, and visible and tiling over will not work.

I am still experimenting with this.  Now, onto new territory for me:

LIMESTONE

How can I be the best possible option for the customer when it comes to limestone fountains?  I would like to carry my knowledge forward, but limestone, and other natural stone is a different beast.  As mentioned, I have read Maurizio's posts along with some other people who at least appear to be experts and once again, I would say I agree for the most part about outdoor stone.  But my applications involve fountains of solid limestone block mortared together in either a constantly submerged (in the basin) or heavily exposed to water otherwise.  Seal just the inside?  Seal inside and out?  Don't seal at all???

The manufacturer recommends a brush/spray on liquid (they cannot include in the containers shipped to U.S.) but it sounds like any other "penetrating" high V.O.C. sealer.  They say inside and outside and reapply once per year.  Sounds familiar to me!

If this was a concrete basin, I could apply any of the tools in my bag of tricks to COVER the inside with a 100% waterproof membrane and go home knowing there will never be a call-back.  But when the original integrity of the stone under all that water has to be maintained, what now?  I am beginning to think that if they want it to be so natural like days of old, than they had best prepare for the problems of that time ... water migration at grout lines, effloressence/mineral deposits where the water sneaks out, etc.

One more thing, FREEZING damage.  I would think a sealer is important.  I have personally seen 4 limestone statues (four seasons ladies) where each one had a small part of her face fall off over two years of freeze thaw here in Seattle area.  Granted they were above a water pond, but not directly exposed.

After all that crap above, it is a lot to chew on so let me summarize:

In spite of the prevailing opinion for outdoor stone, what about my fountain applications?

Concrete fountains:

1.  Seal or not for (a) finish protection and (b) freeze protection

Limestone fountains:

2. Sealant for (a) waterproofing (submersion or otherwise) and (b) freeze damage.

I bill myself as the local expert in my area, and if I am going to do so that means going beyond repeating something I read in a flyer or what someone heard from their dad's cousins foundation layer's son's fountain salesperson.  These people depend on me.  End consumers and up the food chain.  I recieved phone calls from two contractors for the same job 600 miles away about how to handle an install in their area.  Help me back up what I say and put an end to this debate!

Thanks!!!