So research is clear that people will forget if an idea is not revisited every so often. A memorable task will help, but really, you need to review those ideas every so often. This is what interleaving is about, and is at the core of the Making Math Moments ideas on spiraling.
Even if you don’t fully spiral your curriculum, at least bringing up those ideas a week or so later in practice work, or as part of another problem or task, will greatly help the students remember. The closer the idea is to being forgotten when it is recalled, the greater the recall strength gained.
The book “How We Learn” by Benedict Carey, has some great information on the science of learning and more details on the benifets of interleaving. Also, the MMM Academy has a mini course on spiraling, and they spend some time talking about interleaving there, one of their pdf handouts has four or five links to research on interleaving.
I hope this was helpful, as for higher quality tasks, of course the MMM Academy has a task area, the MMM website has a task search engine called the curiosity search engine thats really cool. That should give you some leads to other places to look. Hope you find and figure out exactly what you need to get your students where they should be.