Recently I have been reading the kitaab, Virtues of Salaat and Salaam by Ml Muhammad Zakariyyah Kandhalawi, in which he states we should write salaat and salaam on Rasulullah Sallalahu Allaihi Wassalam in full rather than writing SAW. Using abbreviations is for lazy people, and for as long as the durood remains in a book or perhaps on the pages of a forum like this there will be a malaikah that will constantly send salaat and salaam to Rasullulah Sallalahu Allaihi Wassalam on your behalf.