If you keep your ears clean (obviously), and especially if you keep your hands clean when you handle them, they might be serviceable a bit longer.
If I had to pick one tip for one listening session, it would be the Complys (shorts for my ER6i's and regulars for my Atrio M5s). I try to use new/fresh Complys before a long plane flight or other occasion where I want to have comfort and good sound for a long listening session. But especially if I will be taking the earphones out frequently, the Shures certainly do last much longer (just not quite as comfortable, for me, anyway).
By "platinum," so you mean the gray Complys? They seem to be pretty much the same. Also, as with any foamy, keep yours sealed against the elements -- air will eventually dry them out a bit even if you're not wearing them.