Did I waste time grinding shoe decor in April?

I started pickmin in March 2026 and I grinded pretty hard during the April event and got a lot of the shoes (klompen) decor Pikmin. Now that the event’s over and May has moved on to a new theme, I’m wondering if that was a waste.

Do these monthly event decor sets ever come back in a meaningful way, or should I have just stopped after completing the set? Is there any long-term value in having a lot of duplicates?

I am curious what’s the point of going more than 4 stages when the event pikmins we obtain will just take up the spaces (given that you already collected all kinds for that decor)?