If I use a compression stop I like to leave 1/2' exposed so when the valve does fail the guy who has to deal with it next will be able to get a puller behind the ferrule.I have seen many stops changed where someone couldn't remove the existing nut and ferrule. If I had to I could dremmel it off but there are a lot of plumbers who can"t afford every luxury tool.And the copper that is exposed ,if any,would be polished/sanded.
I have yet to encounter a ferrule I couldn't get off with a pair of Channellocks. I usually use my #426, apply a little pressure on the ferrule, pull toward myself (left forefinger and thumb on the jaws) with a little clockwise rotary motion -- sort of threading it off of the 1/2" hard copper. I have never needed to pull a ferrule off of a piece of soft copper, but I imagine it may not be possible in some cases where the ferrule has distorted the copper so much that the O.D. of the copper and the I.D. of the ferrule just won't allow this method of removal.
In a commercial restroom with heavier traffic, there's much greater chance of impact.
Picture a guy with his 5 yr old, turns to use a urinal and lil' Joey yanks on a feed, spins it very slightly.
Slow drip creates $10K in damage over the weekend 3 months after finish.
Another point already made - spacing.
If the brass is subject to the wrong mineral content in the water and corrodes too quickly, replacement of the stop/compression nut means having to removes the old ferrule as opposed to sweating off the old valve.
Just my opinion.
I always carried a couple of pullers for the nuts and ferrules but in a pinch a handle puller and a PP lav stem will do the trick as well.
"Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony
I never lost a cent on the jobs I didn't get!
I have seen quite a few that the nut split from being overtightened or not tight engough and the stop blew off under high pressure.
I also think a properly soldered one (length of pipe correct) makes for a nicer looking job.
Again, I am not knocking them, I probalby have a few hundred in my warehouse at this moment.
I will say this, my guys will not install a Zurn compression stop, they seem to have had a lot of trouble with them over the years. They only use brasscraft.
doing production work for 15 years, the majority of the stops we used were compression. infact they were the 1 piece not my choice on the 1 piece, but the co's choice.
if i had to use ips threaded stops, i would have never been able to install an average of 400 a day. a compression stop only takes seconds to properly tighten with the proper ratcheting open box flare nut wrench.
i've never had a stop blow off, but i have cracked a few nuts. i always pre prepped the stops with dope or bowl wax on the compression thread to ease the friction of tightening. i also cut the copper at the correct length to give the estucion a finish look.
now on commercial specs. we did use both 1/2'' and 3/8'' ips stops. the slow part is carrying the assortment of brass nipples and preventing the wall insulation from blocking the opening. so this was a lot slower process. plus i had to then carry all the cap ups back to the shop.
as far as removing a nut and ferrule, no problem with a good puller. type l stubs are eaiser as the ferrule doesn't bite as deep as type m copper does.