The usual gamers fallicy...
"Again, the fallacy is the belief that the "universe" somehow carries a memory of past results which tend to favor or disfavor future outcomes."
It's a 20% chance each time you re an item, it's not a 20% chance of all your re attempts.
If it's really a 20% chance, and you do it enough times, the actual results should show something very close to 20%.
The question is, what is "enough times" to prove the 20% out? It's not going to be measured in 100's or even 1,000's. Any statisticians care to answer that?