I would never say anthem is wrong....*_^..but I run my lights on the refugium 24/7...and have since it was first set up. Most information I've seen indicates that a 24/7 photo period may prevent caluperas from going sexual. I do know there are numerous groups that use both methods with sucess(reverse photo period& 24/7)...I prefer the 24/7 option.
As for telling if it is going sexual..as anthem said you will notice it turning white(sort of mushy looking)...kind of like its bleached and lost its color...I check my refugium daily and use a long pair of tweezers to pinch off the white leaves and discard them. I've never had very much go sexual at any one time...but I've heard of it happening. As stated it can pose some serious problems if it happens.