I am a big believer is revising what we have done over and over again to make sure there is true understanding.  For me the key is just to make sure that you find fun ways of doing it so that the concepts stick in the kids brain.

When we first learnt the sh/ th/ ch sounds we had great fun making our sound flowers with the words in the petals

Pink really loved this activity so much so that we now have it hanging on the wall.

I also found these fun penguin and fish words.  I changed the activity slightly, we put a penguin with a sound on a cover of an envelope and then Pink had to read the words on the fish and feed them to correct penguin (ie put the correct word in the correct envelope).

http://thefirstgradeparade.blogspot.co.uk/search/label/penguins

We also found this lovely cutting and sticking worksheet for the sh/th/wh sounds.  It is from the 3 Dinosaur website part of their tooth fairy pack (pink had just lost her first baby tooth so this was a big hit).  We have done a number of these sound pages where you have to stick the word in the correct sound column and they have all be very popular with Pink.