No, 17-characters is the max length — that’s something the developers aren’t going to change without significant advance warning, as there are far too many applications that expect such. The only part I’m not sure about is the exact nature of the 14 trailing characters: The API documentation makes it appear they’re hexadecimal. Visual inspection makes them appear to be BASE64, but in sampling a 10,000-record table, I found no record ID that contained any of the non-alpha, non-numeric characters commonly added to ‘0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz’ for a 63rd and 64th token, so I have to assume it’s BASE62. (The decision to go with 14 significant characters may be GS1 barcode-related — or not…)
Again, I don’t think you need worry about record IDs longer than 17 characters. (In fact, if this was still the 1980s, you’d probably be safe allocating 14 characters per ID and amputating the leading ‘rec’.)
Edit: Since you’re talking about specific storage allocation, I have to assume you’re storing them outside of Airtable. In that case, you may want to check this earlier thread.
