Try to always credit your flights somewhere, although probably not to SQ. Look for programs in which miles don't expire ever (DL for SkyTeam) or that require only minimal/cheap/easy activity to keep the miles alive. Joining FF programs is free and easy; you might someday have enough miles for a free ticket you can use; just try to keep things concentrated in one FF program per alliance or use one that crosses alliances and covers the airlines you use (AS covers AA, CX, and DL currently, among other carriers or one of the ME3 might work for you).