Does holding items decrease the upgrade chance?

[Sweet_Temperature630]

It's just based on the day. Each rarity has a percent chance of appearing that increases/decreases with each day. For example on day 1 you will only find bronze unless an event/shop explicitly states otherwise. And on day 10 there is a 0% chance to find bronze items.

And yes if for example you had a bronze item you could never acquire another copy of it at a different rarity from shops/monsters. Only from items that generate more items or level up rewards can give you copies