Heres some info from the Merck Vet Manual about Giardia.
http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/21300.
I think that yearly checks for giardia is a little much. Like the manual says we usually look for giardia when a young dog comes in with diarrhea. We collect a stool sample (for Giardia a fresh sample is preferred) set up a float and also a direct. I actually just looked at a giardia sample taken from a puppy and Doctor Mark said its also hard to find the protozoa because after exposed to light for an amount of time the giardia loose its mobility and is hard to tell the difference from regular cells in the stool.
The manual says that treatment with fenbendazole (panacur) is used this also deworms for a number of different zoonotic parasites. Which you should discuss with your vet when doing boosters and every couple of week check ups. According to the CAPC your vet should "Conduct fecal examinations two or four times during the first year of life and one to two times per year in adults, depending on patient health and lifestyle factors." http://www.capcvet.org/recommendations/guidelines.html
