I have no idea what you are observing and what in this respect should be "normal" or "recovery time", but if I enable Loop Detection on my TL-SG108E and create a loop, it blocks the port with the higher number and shows this blocking by blinking both (green and amber) LEDs every second or so. Only traffic on this port is the probe package of the switch needed to detect this loop, and yes, this will be sent about every second:





I can't see a "broadcast storm" either on my switch. Why would you want to extend this time to 300 seconds? This is no "recovery", this is just a probe package sent out by the switch. A real "recovery" would be to remove the loop ASAP after it has been detected and that's the only meaningful action to take in such case.