How do hearts work?

[Eren]

Ive been playing for ages (day 120 now) and once I completed the storylines Ive been having more days earning no hearts. Barely any orders (almost always 1 or 2 a day, usually only ordering one or two sticker types and never my new ones which makes me sad) and it's been making it really hard to get more hearts. Ive been giving lollies and freebie stickers but it doesnt seem to help that much. Im really confused as to how gaining hearts actually works so any tips would be helpful- and if theres any way to get them to buy new stickers. It makes me sad that so many stickers I spent ages on and love just sell none while one sells almost always and another 3 are also super popular despite being some of the first couple I made

[Aseruff Trazu]

Hearts are generated when a sticker that isn't maxed out reaches a new stage of star. (So 5 star assets won't generate hearts anymore)

In order to have people stop ordering the stickers that had maxed out all the assets, I removed them from my shop listing, forcing the customers to use the new ones in order to generate hearts more reliably so that I could complete obtaining all the stickers.

I also created a couple of stickers using almost solely assets that I hadn't used prior, which got some interesting results, but worked on getting me enough hearts in the end.

Now I just hide the ones I don't actively want to print and package and unhide the ones I like the most. (Rotating through the stock based on my own moods and deleting any stickers I made solely for the assets)