It is not that rational, but I'm sure this behavior is not so rare... and in that sense, "normal". I show signs of it myself, too.
But I think that's more or less typical collector's behaviour, and not limited to porn collectors.
Do movie buffs watch all the DVDs or movie downloads they get immediately, and then get the next one? And only afterwards they look for the next one?
Do anime fans watch all the series immediately?
I don't think so; in my experience there are people who hoard a lot of stuff on their harddrives and rarely get to watch it, and probably will never have enough time to watch it completely.
If it's "crazy" then the craziness lies in the crazy amount of supply we modern people have to get entertained. There's more stuff than we ever could read, watch, or listen to in our lifetimes; and the seemingly more rational option, "to choose more strictly" is also more difficult because you have to make an effort to think about your choose. Thus the option "I collect more and more, and delay choosing what I really will watch, and in the meantime I'm gonna have fun with collecting even more" is easier.
Your point that the joy of anticipation beats the joy of fulfillment is also correct, of course.
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