I'm wondering what exactly this is as pertaining to paypal, and when it comes into effect (how many claims)
Visa and Mastercard liability for a transaction to be charged back is 180 days. Paypal passes this length of time onto paypal users when they hold funds. Basically they can hold your funds for a max of 180 days. After that Paypal is no longer liable for that money so you would get your money back.