At least 217 feet.
Please keep in mind this is an Ultra High Frequency UHF Gen 2 RFID tag meant for use in item sales, tracking, and inventory. This is not the same RF technology in use by access cards. Those are generally Low Frequency (LF) and have a much longer wavelength, which results in a shorter demonstrated distance of 12-19 inches, although that is much farther than the distance claimed by the access card vendors in the interests of system security. Most door badge readers are designed to require a distance of less than two inches.
Near Field Communications (NFC), found in credit cards, cell phones, and other payment systems, use High Frequency (HF) which falls in-between the two, and they will have a range somewhere between the two. They have an intended operating range of only a few inches, but with an antenna and receiver designed to read them, they may have a much longer eavesdropping range, probably in the 10 foot range. I don't know of specific experiments in distance eavesdropping on credit cards from long ranges; most such attacks have been demonstrated by disguising the reader in a backpack and reading victims' cards through their wallet on a bus or train.
Also, you should not discount specific antenna or receiver technology. If there is value to be had in scanning an RFID tag from across a parking lot (surveillance of a person, that sort of thing) then you can be assured that someone will find a way to abuse it to obtain that value illicitly. They may hide the antenna in a canvas-sided truck to commit their surveillance.
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Because an RF reader can read tags at 5m is doesn't mean it can do so for a passive tag. I'm saying this because the reader specification may be referring to an active tag i.e. one that contains a battery and is able to wake up when it detects the smallest "proximity field" from the reader.
So, once you've got that firmed up, adjusting the range to 1m (and this is usually done by lowering the "proximity field"), may give variable results - some may work outside 1m and some may not work until well-inside the 1m range.
I'm assuming your question is "What factors should be considered when reading a tag at a certain distance".
A tag relies on a wake-up field (or proximity field) to activate it and, the detected level of this field will vary from tag to tag - it's worse for passive tags because they are energy harvesting the field in order to create enough internal supply voltage for them to transmit a response and therefore there are more factors that can vary when energy harvesting.
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