At the moment the only data available to us is the current state of the pledge plus the total_historical_amout_cents value which represents the lifetime value of a pledge (less refunds). You would need to build a system that is responsible for keeping track of the state of each pledge if you wish to know things like “how long has this patron had this reward?”. Depending on the level of information you need you may be able to make this system just using webhooks however if you need payment status information then you’d need to build out a system that requests data from Patreon routinely (as webhooks are only made for user-initiated status changes; not automated (i.e payment)).
You can also find a bunch of information about how the Patreon system works provided by the Patreon team in the following 2 topics, which was helpful for me when building a system similar to the one you describe: