In I.B.S. and N.B.R.S.A. registered Benchrest competion, the rules specify a minimum amount of time between each relay.
If for example, you are on Relay #1 and the rulebook shows 30 minutes between relays, you will have at least 30 minutes before your relay is called back to the firing line. Relay #2 will be shooting in that 30 minute time frame. If you have more than two relays, you'll have at least an hour. If there's only one relay, you'll have at least 30 minutes.
NBRSA rule book... 11) on page 26. at least 30 min. between your relays.
but most of the time it's longer. they will wait on you. cause they are nice guys !!! you can go to the rule book web site and read for HOURS. just have fun.