a) there'd be an awful lot of abstract data to handle
b) if you could handle that much abstract data, you could also manipulate it for eternal youth or the like, or create copies, or store it for immortality
Unfortunately, "Our Man Bashir" totally eliminates any concerns about storage of the data, so apparently these two first problems are "solved." The computer aboard Deep Space Nine can store at least 5 patterns indefinitely even after the pattern buffer matter stream has totally degraded. If they can store five, they can copy at least two - at least as far as data storage concerns go.
I'd venture to say that Star Trek's typical excuse of not being able to "store so much data" flies in the face of everything we've seen them do with a transporter.
Of course, they wouldn't even need any of that to offer people eternal youth. Just find a Galaxy class starship transporter system and program it to remove the RVN sequences from the person's DNA and you can send them right back to puberty.