Most music teachers will encourage you to practice your instrument every day. But why? Are you rehearsing for a public performance? Are you a musician by trade? Assuming you're learning the ukulele for fun or as a new hobby, I'd much prefer you played what you want, when you want. I truly want the ukulele to be a source of joy for my students (and everyone!). And when was the last time you felt joy completing a homework assignment?!?*
Your relationship with your uke will be happier and more sustaining if you play when you feel intrinsically motivated to play. Even if that means you're only playing once in a while. I pick up my uke for any number of reasons— to provide entertainment for my kids, to create with others, because I want to try out something new, or (most often) because it's fun. What motivates you to play?
* For the occasional student who insists on assignments, I tell them to simply pick up their instrument every day.