Newports chart only shows around 3.5 years worth of the latest data, you can go back, but that only shows the first 3.5 years of data. i.e. you won't see the full graph/chart range for anything that has > 7 years of historic weekly data (only the first and last 3.5 years). And I think Newport stalls once there's more than ten years of data recorded (or perhaps a bit less as (guessing) 10 years x 52 weeks = 520 and I suspect it might be a 512 (binary) limit).
The standard approach once you get up to those sorts of length of history is to cut out the middle section of stored data so that Newport keeps running OK i.e. has the early/first years, and the more recent years.
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