I don't think it really is that you have a long
gap when you rewrite
a "bad" block per se. But you get long gaps when you stop/start. And
a rewrite implies that you will get a stop/start situation. But in
case you already were going stop/start, the gap will not be extended
any longer.
Some drives will back up, get up to speed, read the end of the previous
block, switch from write to read when the irg goes by.
The size of the irg can vary upwards from a minimum spec, at least in
drives that try to stream, as they will keep the tape running for a
moment in hopes that data will arrive to be written.
De