Every 2-3 days or so, depending on child's interest! Of course refresh activities if needed, unless your child wants to add to it the next day.
These can match whatever theme you can think of! Holidays, book themes, characters, you name it!
There are TONS of free, printable templates online. The trickiest part is finding ones that match the size of pattern blocks you have at home!
Symmetry match
Pattern cards
Roll & Build
Can you build... ?