Anyone loving Korean skincare? How long to see results?

I've been doing quite a bit of reading about it and am debating a full switch after twenty years. I have always had a good wash routine, wear sunscreen, and get facials when I can afford them. But overall my face just doesn't look good. It's just dull and it makes me look and feel so old. I did dip my toe in the water with Isntree's Sun Gel and did like how much lighter it was. My usual products are running out so I'm pondering switching my entire routine to their line but am wondering what is a realistic timeframe to expect results. Would love to hear thoughts from anyone here.