Subscribe for the amount of time that you have been a follower, e.g. say you have been following someone for 62 months but couldn't afford to subscribe until recently, give us the option to subscribe for the past 62 months, get the sub-badge, and pay the streamer for the past 62 months that you have been a continuous follower. not sure how it would work if you had gift subs/twitch prime randomly throughout the time you followed them, maybe just ignore it and and make it a running total for the entire time.