A notification pops up when I resub, but if I miss it since it only lasts a couple weeks then I don't see any other way to check.
How wide can the difference be between the creation date and real subscription time? How wide can the difference be between the creation date and real subscription time? If the streamer can't recognize that you've been there since Day 1 without the little text reminder, then I highly doubt they really value you at all.