Gentlemen - thanks for your responses. Although I am not prone to lightning surges where I live, there is a possibility of other types of surges (faults etc).
Once the warranty expires, the SA will likely still work, but there is no guarantee. To me, that defeats the purpose of getting the SA in the first place.
@erik_squires - thanks for the info on the Siemens SA's - does look like they have a 10 yr warranty, but I couldn't find info on $ coverages - I will do further research. I don't think that my electric utility offers surge protection - I'll have to inquire.