I personally don't have any problem with this any more than I had a problem with people hoarding effigies, as long as the overall exp rate is not unreasonably high. And in this case it's not. To name a few more, you can also hoard sq'irk juice, temple trekking xp books, Brimhaven tickets, long/curved bones, and Brianpoints. The important thing is that it should still be better to actually train your skills, which is why they nerfed the flash powder factory and effigy drop rates. Perhaps players should have questioned their logic when they limited effigies to 5 in the first place.
"The only thing an adult can give a child is a yellow cape." - Chuck Jones