For mana cycle I usually take 15 seconds (So he is always on)
BTW for the buffs like Pain Quota etc. you can better take a little higher delay, because you can't cast them if they already casted. If you want to be sure that every members is buffed, choose your delay then wisely.
EXAMPLE:
Physical Fence, normal delay is 1800 seconds
Take a 2-minute-delay, iBot Tool will try to cast the buff every 2 minutes, this will fail when the buff is already casted, but that's not a problem (he won't disappear), if the buff isn't casted yet, he will just give it again. (If someone died for example). But 30minutes/2= 15; So he will try it 15 times, if everything goes well, it just recast the buff after 30 minutes. I hope I made it a little bit more clear now. :)