WordPress Points System

Hello, I got someone to set up a ecommerce website for me and he made a points system where the vendor uses 1-25 points to post a product on my site. They make a payment in my account and I add the points to their account and then it deducts the points depending on how much their product is being listed for. it is kinda like the percentage thing just with full points instead of a percentage. and it is only available in my country, which is pretty small. But I would like the points to expire 30 days after I give the points to them. but if I add points to their account before the 30 days is up then their previous points will expire the same time their new points do. what coding would I need to add or how would I get this done?

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