I use the NFS tag and have been guilty of later selling them. I try to avoid selling them but, if I'm selling a ANFS for sale cel/sketch it means I really need the cash. It's not that I just got bored with it or that someone offered me an insane ammount for it. There are a number of the ANFS cels I've turned down offers on that the offer has been more than $1k over what I paid and there are at least a few pieces I can think of that honestly, are not for sale at any price ever. Someone could seriously offer me $1 Million dollars and I would not sell them because they have meaning beyond being painted plastic.
But, generally speaking if I slapped the NFS tag on something, at that moment in time I have zero intention of selling. However, my family comes before my art collection so if I have to sell something it breaks my heart to sell I'll do it if I must. And I have in the past there are a few pieces I sold and pine for still I don't regret selling them because of what needed to be done. I wish I had the sort of income that would allow me to not sell things when I get in a nasty situation but, I don't we can only buy things through very careful budgetting at this point our mortgage and Bills take up about 90% of our income. So we buy art rarely now and when we do it usually has to be funded through the sale of our other pieces. And if we have a large issue of some sort (like unexpected $600 worth of car repairs recently). We live on our own of our own means and our parents aren't going to fix it for us (my parents are totally financially unable and Jen's...well that's long story). So if it comes down to it I'm apt to sell what's the most valuable so I can do what needs to be done.
Besides that I'm sure people change their minds everyone goes through collecting phases and sometimes you go through a phase where you do a lot of impulse purchases love them and then realize oh hey I don't really need all this do I?
The other reason I use them is because I like to avoid getting asked about the same cel again and again. There are a few shots I don't have any plans to sell in the near future or far flung future but people ask about them pretty consistantly and while it's flattering I'd rather just try and nip in the but, rather than constantly saying no. Which isn't to say I'm offened by the offers or anything. I just would like to quell them a bit. I'm always polite about answering them as I understand how seeing your dream cel in someone elses gallery feels but, again it gets to where you don't even want to display the things anymore.
As far as seeing the ANFS/NFS in other people's galleries I generally respect them (though there a few times that I have asked anyway in blind hope or sent a
if you change your mind please let me know meddage) . I rarely offer on anything anyway unless someone is in an offer period because, it always feels kind of wrong to me. Not that I won't do it if there's a high end wishlist cel sitting there. I find collecting is often a paradox like that for me though, it makes me engage in activites I would never bother with on a normal basis.
Mwhahaha!
. I use both the NFS and ANFS, and to tell the truth I genuinely don't want to sell those items and the use of those labels are to discourage people from asking. I don't like saying "no" very often, so this just makes things a little easier for me, so I feel less like an @#%. I did part with a few NFS items not so long ago to fund a wishlist item, but overall those are the items I'm looking to keep in the collection for years to come. So I use them and will probably continue to use them, though I can see why it's frustrating 
