https://www.dekudeals.com/ is your best bet IMO. You can set up wishlists there and get notified of price drops. You can also see the price history of games for the last few months, so if something regularly goes on deep discount every 6 weeks you can see the patterns and hold out.
However, if it's first-party Nintendo games you're after, I wouldn't be holding out too much for big sales discounts.
https://www.dekudeals.com/ is your best bet IMO. You can set up wishlists there and get notified of price drops. You can also see the price history of games for the last few months, so if something regularly goes on deep discount every 6 weeks you can see the patterns and hold out.
However, if it's first-party Nintendo games you're after, I wouldn't be holding out too much for big sales discounts.