Diff breather manifold required?

If you had a short length of hose on the open port, am I right that you could to blow into the hose periodically check the other ends havent come off? I cant see myself getting under the car to regularly check them, except on 4x4 weekends.

EDIT: I see this is possible upon further reading. Thanks anyway. 

Is the black seal in Diff removed when fitting the breather?

I fitted these 8 years ago and never had an hose disconnect 
It's a 1/8 bsp elbow to 6mm od pipe 
Removed the cap and tapped the stub 1/8th bsp taper tap no drilling needed 
Just used grease and a strong magnet on the tap so swarf stayed on the tap 

Im not going to do this given the car is under warranty still, but wondering if its possible to drill an access hole in the floor pan and use that to tap the transfer case spigot?

Just my thoughts, but, if warranty coverage is your concern, forget about cutting a hole in the floor for a moment - how would your dealer view the fitting of extended breathers from a warranty perspective?

To be honest, I haven't looked to see where the transfer case breather is to determine how feasible the idea of cutting a hole in the floor is, you would need to mark the hole center with a reasonable degree of accuracy and then find a rubber bung or similar to close the hole once the breather has been fitted, but I see this as less of a "warranty voiding" issue than the tapping of the transfer case.

The danger of swarf from the tapping exercise entering the transfer case is greater than any possible damage done by carefully cutting a hole in the floor.

Cutting a hole in the floor is not as simple as you might imagine, you're going to need to remove the carpet, and that pretty much means gutting the interior, all the seats have to come out as well as a significant portion of the interior trim, which I have done, because I added sound deadening material to the interior - personally I think dropping the transfer case is easier, and then I can lay it on the side and tap the hole, reducing the chances of swarf entering.

You could be opening yourself up to all sorts of dealer issues if you do anything to the breathers.

The transfer case on my Gen 4 was fairly easy to do with the rear wheels on ramps and the clamp kit I used was straight forward to fit.

Plus, it would be possible to refit the original breather valves if there was ever an issue and I doubt anyone, even the dealer would know.

Robin