Renato mentioned they are reset as and when needed for specific cars. If a car has been slowed down with an update and the lap times are no longer achievable the LB should be wiped.
Oh man I really hope they reset the F-Reiza LBs where I cannot follow the leaders ByTheWay: I just gonna check this out
Phuiii. I just checked the many F-Reiza LBs where Im in the leading group - and Reiza have not reset any of them. Thank youu Reiza