Hi Friends!
Like many of you, I too am an avid fan of Membership and Discount cards. I have a lot in my wallet but I don't get to use all.
The cards that I regularly use though are:
Robinson's Rewards card - For groceries and department store purchases
SM Advantage card - For the same, but not as frequent since Robinson's is more proximal to where I live
Mercury Suki card - For medical purchases. I have twice redeemed the annual planner-ish notebook that they offer at the end of each year. I used it as a personal health check notebook where I jot down vitamins or medicines I take. I found no use to get another one for 2015 and still use my 2014 one.
Shopwise Wise card - Used this a lot when I was still working in Makati. I let my fiance use it for now for his groceries.
Belle de Jour Lifestyle card 2015 - I got this free with the BDJ Planner but rarely to never use it. They have this zap points that you have to register for first. I tried it once at a milk tea shop in Greenbelt (I forgot the name of the shop LOL) and it took me a long time to get my zap points
7-Eleven Every Day! Rewards - because this store is sprouting out just about everywhere, God knows how many times I have used this card. Still haven't availed of any discounts, promos or used any points for this...
Medicard HMO card - Company HMO. I have yet to try out their benefits and discounts at other establishments though so fingers crossed with that
South Star Drug Tipid Kard - I have not availed of anything from them yet nor have I redeemed any points so can't say much about it.
Shakeys Supercard - I got this free with one of their group meals. Good deal with the free pizzas and birthday pizza
Other cards I have tried/have:
Laking National - Though I do buy some things from National bookstore, I don't go there enough times a year to make most of the card, so I just didn't renew it anymore.
Intellicare - Company HMO a couple of years back
Cebuana Lhuillier - 24K Card - I used to use Cebuana a lot for money transfers when I would pay for bulk orders from suppliers. I don't use it as much now but when the cashier said that the new card would be permanent, na persuade ako haha
HBC Exclusives Card - I used to hoard HBC products a lot in the past but have not been doing so much lately. I have availed their free facials.
Starbucks Card - Truth be told, I seldom to never go to Starbucks and just got this card as a gift. I used to love Starbucks but grew out of the hype. Vendo coffee is good enough. I did however get a free grande latte and still waiting for my birthday to claim my free slice of cake

I heard the points don't expire so neither does the card, I think? Been using it 2 years running only during their buy 1 take 1 coffee days or promo days hihi

Cards I am considering:
Get Go Membership card - My fiance and I love traveling and might as well pile up on some free miles!
Baby Company Mom card - Planning to get this once I get pregnant again

My rule with membership and discount cards is simple. If I regularly visit the store then sulit siya. If not don't bother unless they give it free with a certain purchase amount. I am not a big fan of cards that charge kung di naman ako madalas bumili o magvisit sa store.