Both recipes and implings are common from the maw. The maw will always give you the lowest impling you've yet to catch. So yeah, assuming you are slowly doing moss anyway, there is no particular need to rush those things. I got my last impling (crystal) from the maw today, for example. Still 12 draws from the maw with zero recipes :( I got Kingly from Maw today however I only need Crystal Imp, so won't always give you the lowest imp you need.