Instant Savings!
A bird in hand is better than two in the bush.
To do progressive type/preferred customer discount on items I MIGHT purchase every few YEARS doesn't help me as a customer unless it is understood that there is to be no time limit on the discounts.
I buy the best gear I can afford at the time and my buy it for the long haul! I don't get a different bike every year and my gear is the same. I'm not a bike night,motorcycle gear trend Setta!

nfloor
That doesn't mean there's anything wrong with giving the same level of discount when someone is buying high end/higher cost items or multiple items at one time and earn progressive discounts.
Those purchases should be rewarded/discounted at the same rate or maybe even more as some one who purchases the same dollar amount but say over a few months/one years time.
If you put a time limit on how long this progressive points earning program is for that just turns people off if they aren't able to purchase something and then they lose the discount. That would make me feel like I missed out,missed an opportunity,make me feel bad. You want customers to feel good when they think about your business,not bad or that they missed out. What you now have is a marketing game,a gimmick and you want someone to buy something from you,but not a real customer. There's a difference between the two.
You use gimmicks to sell stuff and it doesn't matter to who you and you use mutual business relations to keep them comming back. A carny at a county fair uses gimmicks to sell a "mark" a load of B.S. to get them to spend their money and really doesn't care if that person feels they got ripped off or not.Chances are they will never cross paths again.
Think about it for a moment you want a customer to be loyal and lifelong right?
OK,well when a company tells that same customer "Oh yeah,by the way uh..you only have X amount of time to use the credits/points you've earned or else you lose them". What your REALLY telling that customer is "Yeah,we want your loyalty,business and we WILL give you a progressive discount on future purchases,but it contingent on a time limit." Does your PERSONAL relationships have specific,built in time limits? Of course not and neither should your business relationships.
You have now just alienated that prospective lifelong customer and lumped them into the buy it and get out crowd. You know who I mean the squids that think they are real BIKERS. Buy a new bike,buy all new matching gear,crash said bike or get it repossessed in the first year...never ride a bike again. THAT'S not the customer you NEED to cater to as they won't be with you for years and years down the road. Stuff happens and there are eb and flows,good times and bad. Sometimes people have a run of good fortune and they will often times remember who stuck by them and who brushed them off. It's the same in business and your in a dog-eat-dog,retail,sell to the public business. The businesses that have the best,repeat,with you for the long haul customers,are the ones that come out and more importantly STAY on top.
Bottom line if you provide a balance of the best service,best prices,best products,best no-hassle return policy etc. buyers tend to stay loyal to the business that provides that.
We have very successful locally owned shoe store in Bloomington,In. that has a return customer discounting system,but they also apply purchases of even sale/discounted/close out items toward the system. So there are times when customers get a good deal on selected items AND it goes toward future purchases as well. They aren't a fly-by night,flash-in the pan type of store. They are a part of the community and have been for a long time and their customer loyalty reflect this.